Amylase Variants

ABSTRACT

The present invention relates to variants of a parent α-amylase, which parent α-amylase (i) has an amino acid sequence selected from the amino acid sequences shown in SEQ ID No. 1, SEQ ID No. 2, SEQ ID No. 3, and SEQ ID No. 7, respectively; or (ii) displays at least 80% homology with one or more of these amino acid sequences; and/or displays immunological cross-reactivity with an antibody raised against an α-amylase having one of these amino acid sequences; and/or is encoded by a DNA sequence which hybridizes with the same probe as a DNA sequence encoding an α-amylase having one of these amino acid sequences; in which variant: 
     (a) at least one amino acid residue of the parent α-amylase has been deleted; and/or
 
(b) at least one amino acid residue of the parent α-amylase has been replaced by a different amino acid residue; and/or
 
(c) at least one amino acid residue has been inserted relative to the parent α-amylase; the variant having α-amylase activity and exhibiting at least one of the following properties relative to the parent α-amylase: increased thermostability; increased stability towards oxidation; and reduced Ca 2+  dependency;
 
with the proviso that the amino acid sequence of the variant is not identical to any of the amino acid sequences shown in SEQ ID No. 1, SEQ ID No. 2, SEQ ID No. 3 and SEQ ID No. 7, respectively.

FIELD OF THE INVENTION

The present invention relates to α-amylase variants having improvedproperties relative to the parent enzyme (e.g. improved thermal and/oroxidation stability and/or reduced calcium ion dependency), and therebyimproved washing and/or dishwashing (and/or textile desizing)performance. The invention also relates to DNA constructs encoding thevariants, and to vectors and cells harboring the DNA constructs. Theinvention further relates to methods of producing the amylase variants,and to detergent additives and detergent compositions comprising theamylase variants. Furthermore, the invention relates to the use of theamylase variants for textile desizing.

BACKGROUND OF THE INVENTION

α-Amylase enzymes have been used industrially for a number of years andfor a variety of different purposes, the most important of which arestarch liquefaction, textile desizing, starch modification in the paperand pulp industry, and for brewing and baking. A further use ofα-amylases which is becoming increasingly important is the removal ofstarchy stains during washing or dishwashing.

In recent years attempts have been made to construct α-amylase variantshaving improved properties with respect to specific uses such as starchliquefaction and textile desizing.

For instance, U.S. Pat. No. 5,093,257 discloses chimeric α-amylasescomprising an N-terminal part of a B. stearothermophilus α-amylase and aC-terminal part of a B. licheniformis α-amylase. The chimeric α-amylasesare stated to have unique properties, such as a differentthermostability, as compared to their parent α-amylase. However, all ofthe specifically described chimeric α-amylases were shown to have adecreased enzymatic activity as compared to their parent α-amylases.

EP 252 666 describes hybrid amylases of the general formula Q-R-L, inwhich Q is a N-terminal polypeptide residue of from 55 to 60 amino acidresidues which is at least 75% homologous to the 57 N-terminal aminoacid residues of a specified α-amylase from B. amyloliquefaciens, R is aspecified polypeptide, and L is a C-terminal polypeptide comprising from390 to 400 amino acid residues which is at least 75% homologous to the395 C-terminal amino acid residues of a specified B. licheniformisα-amylase.

Suzuki et al. (1989) disclose chimeric α-amylases, in which specifiedregions of a B. amyloliquefaciens α-amylase have been substituted forthe corresponding regions of a B. licheniformis α-amylase. The chimericα-amylases were constructed with the purpose of identifying regionsresponsible for thermostability. Such regions were found to includeamino acid residues 177-186 and amino acid residues 255-270 of the B.amyloliquefaciens α-amylase. The alterations of amino acid residues inthe chimeric α-amylases did not seem to affect properties of the enzymesother than their thermostability.

WO 91/00353 discloses α-amylase mutants which differ from their parentα-amylase in at least one amino acid residue. The α-amylase mutantsdisclosed in said patent application are stated to exhibit improvedproperties for application in the degradation of starch and/or textiledesizing due to their amino acid substitutions. Some of the mutantsexhibit improved stability, but no improvements in enzymatic activitywere reported or indicated. The only mutants exemplified are preparedfrom a parent B. licheniformis α-amylase and carry one of the followingmutations: H133Y or H133Y+T149I. Another suggested mutation is A111T.

FR 2,676,456 discloses mutants of the B. licheniformis α-amylase, inwhich an amino acid residue in the proximity of His 133 and/or an aminoacid residue in the proximity of Ala 209 have been replaced by a morehydrophobic amino acid residue. The resulting α-amylase mutants arestated to have an improved thermostability and to be useful in thetextile, paper, brewing and starch liquefaction industry.

EP 285 123 discloses a method of performing random mutagenesis of anucleotide sequence. As an example of such sequence a nucleotidesequence encoding a B. stearothermophilus α-amylase is mentioned. Whenmutated, an α-amylase variant having improved activity at low pH valuesis obtained.

In none of the above references is it mentioned or even suggested thatα-amylase mutants may be constructed which have improved properties withrespect to the detergent industry.

EP 525 610 relates to mutant enzymes having improved stability towardsionic tensides (surfactants). The mutant enzymes have been produced byreplacing an amino acid residue in the surface part of the parent enzymewith another amino acid residue. The only mutant enzyme specificallydescribed in EP 525 610 is a protease. Amylase is mentioned as anexample of an enzyme which may obtain an improved stability towardsionic tensides, but the type of amylase, its origin or specificmutations are not specified.

WO 94/02597 discloses α-amylase mutants which exhibit improved stabilityand activity in the presence of oxidizing agents. In the mutantα-amylases, one or more methionine residues have been replaced withamino acid residues different from Cys and Met. The α-amylase mutantsare stated to be useful as detergent and/or dishwashing additives aswell as for textile desizing.

WO 94/18314 discloses oxidatively stable α-amylase mutants, includingmutations in the M197 position of B. licheniformis α-amylase.

EP 368 341 describes the use of pullulanase and other amylolytic enzymesoptionally in combination with an α-amylase for washing and dishwashing.

An object of the present invention is to provide α-amylase variantswhich—relative to their parent α-amylase—possess improved properties ofimportance, inter alia, in relation to the washing and/or dishwashingperformance of the variants in question, e.g. increased thermalstability, increased stability towards oxidation, reduced dependency onCa²⁺ ion and/or improved stability or activity in the pH region ofrelevance in, e.g., laundry washing or dishwashing. Such variantα-amylases have the advantage, among others, that they may be employedin a lower dosage than their parent α-amylase. Furthermore, theα-amylase variants may be able to remove starchy stains which cannot, orcan only with difficulty, be removed by α-amylase detergent enzymesknown today.

BRIEF DISCLOSURE OF THE INVENTION

A goal of the work underlying the present invention was to improve, ifpossible, the stability of, inter alia, particular α-amylases which areobtainable from Bacillus strains and which themselves had been selectedon the basis of their starch removal performance in alkaline media (suchas in detergent solutions as typically employed in laundry washing ordishwashing) relative to many of the currently commercially availableα-amylases. In this connection, the present inventors have surprisinglyfound that it is in fact possible to improve properties of the typesmentioned earlier (vide supra) of such a parent α-amylase by judicialmodification of one or more amino acid residues in various regions ofthe amino acid sequence of the parent α-amylase. The present inventionis based on this finding.

Accordingly, in a first aspect the present invention relates to variantsof a parent α-amylase, the parent α-amylase in question being one which:

i) has one of the amino acid sequences shown in SEQ ID No. 1, SEQ ID No.2, SEQ ID No. 3 and SEQ ID No. 7, respectively, herein; or

ii) displays at least 80% homology with one or more of the amino acidsequences shown in SEQ ID No. 1, SEQ ID No. 2, SEQ ID No. 3 and SEQ IDNo. 7; and/or displays immunological cross-reactivity with an antibodyraised against an α-amylase having one of the amino acid sequences shownin SEQ ID No. 1, SEQ ID No. 2, SEQ ID No. 3 and SEQ ID No. 7,respectively; and/or is encoded by a DNA sequence which hybridizes withthe same probe as a DNA sequence encoding an α-amylase having one of theamino acid sequences shown in SEQ ID No. 1, SEQ ID No. 2, SEQ ID No. 3and SEQ ID No. 7, respectively.

An α-amylase variant of the invention is subject to the proviso that itis a variant which does not have an amino acid sequence identical to theamino acid sequence shown in SEQ ID No. 1, in SEQ ID No. 2, in SEQ IDNo. 3 or in SEQ ID No. 7.

DNA sequences encoding the first three of the α-amylase amino acidsequences in question are shown in SEQ ID No. 4 (encoding the amino acidsequence shown in SEQ ID No. 1), SEQ ID No. 5 (encoding the amino acidsequence shown in SEQ ID No. 2) and SEQ ID No. 6 (encoding the aminoacid sequence shown in SEQ ID No. 3).

The amino acid sequences of the SEQ ID No. 1 and SEQ ID No. 2 parentα-amylases, and the corresponding DNA sequences (SEQ ID No. 4 and SEQ IDNo. 5, respectively) are also disclosed in WO 95/26397 (under the sameSEQ ID Nos. as in the present application).

The variants of the invention are variants in which: (a) at least oneamino acid residue of the parent α-amylase has been deleted; and/or (b)at least one amino acid residue of the parent α-amylase has beenreplaced (i.e. substituted) by a different amino acid residue; and/or(c) at least one amino acid residue has been inserted relative to theparent α-amylase. The variants in question have themselves α-amylaseactivity and exhibit at least one of the following properties relativeto the parent α-amylase:

increased thermostability, i.e. satisfactory retention of enzymaticactivity at a temperature higher than that suitable for use with theparent enzyme;

increased oxidation stability, i.e. increased resistance to degradationby oxidants (such as oxygen, oxidizing bleaching agents and the like);

reduced Ca²⁺ dependency, i.e. the ability to function satisfactorily inthe presence of a lower Ca²⁺ concentration than in the case of theparent α-amylase. α-Amylases with such reduced Ca²⁺ dependency arehighly desirable for use in detergent compositions, since suchcompositions typically contain relatively large amounts of substances(such as phosphates, EDTA and the like) which bind calcium ionsstrongly.

Examples of other desirable improvements or modifications of properties(relative to the parent α-amylase in question) which may be achievedwith a variant according to the invention are:

increased stability and/or α-amylolytic activity at neutral torelatively high pH values, e.g. at pH values in the range of 7-10.5,such as in the range of 8.5-10.5;

increased α-amylolytic activity at relatively high temperatures, e.g.temperatures in the range of 40-70° C.;

increase or decrease of the isoelectric point (pI) so as to better matchthe pI value for the α-amylase variant in question to the pH of themedium (e.g. a laundry washing medium, dishwashing medium ortextile-desizing medium) in which the variant is to be employed (videinfra); and

improved binding of a particular type of substrate, improved specificitytowards a substrate, and/or improved specificity with respect tocleavage (hydrolysis) of substrate.

An amino acid sequence is considered to be X % homologous to the parentα-amylase if a comparison of the respective amino acid sequences,performed via known algorithms, such as the one described by Lipman andPearson in Science 227 (1985) p. 1435, reveals an identity of X %. TheGAP computer program from the GCG package, version 7.3 (June 1993), maysuitably be used, employing default values for GAP penalties [GeneticComputer Group (1991) Programme Manual for the GCG Package, version 7,575 Science Drive, Madison, Wis., USA 53711].

In the context of the present invention, “improved performance” as usedin connection with washing and dishwashing is, as already indicatedabove, intended to mean improved removal of starchy stains, i.e. stainscontaining starch, during washing or dishwashing, respectively. Theperformance may be determined in conventional washing and dishwashingexperiments and the improvement evaluated as a comparison with theperformance of the parent α-amylase in question. An example of asmall-scale “mini dishwashing test” which can be used an indicator ofdishwashing performance is described in the Experimental section, below.

It will be understood that a variety of different characteristics of anα-amylase variant, including specific activity, substrate specificity,K_(m) (the so-called “Michaelis constant” in the Michaelis-Mentenequation), V_(max) [the maximum rate (plateau value) of conversion of agiven substrate determined on the basis of the Michaelis-Mentenequation], pI, pH optimum, temperature optimum, thermoactivation,stability towards oxidants or surfactants (e.g. in detergents), etc.,taken alone or in combination, can contribute to improved performance.The skilled person will be aware that the performance of the variantcannot, alone, be predicted on the basis of the above characteristics,but would have to be accompanied by washing and/or dishwashingperformance tests.

In further aspects the invention relates to a DNA construct comprising aDNA sequence encoding an α-amylase variant of the invention, arecombinant expression vector carrying the DNA construct, a cell whichis transformed with the DNA construct or the vector, as well as a methodof producing an α-amylase variant by culturing such a cell underconditions conducive to the production of the α-amylase variant, afterwhich the α-amylase variant is recovered from the culture.

In a further aspect the invention relates to a method of preparing avariant of a parent α-amylase which by virtue of its improved propertiesas described above exhibits improved washing and/or dishwashingperformance as compared to the parent α-amylase. This method comprises

a) constructing a population of cells containing genes encoding variantsof said parent α-amylase,

b) screening the population of cells for α-amylase activity underconditions simulating at least one washing and/or dishwashing condition,

c) isolating a cell from the population containing a gene encoding avariant of said parent α-amylase which has improved activity as comparedwith the parent α-amylase under the conditions selected in step b),

d) culturing the cell isolated in step c) under suitable conditions inan appropriate culture medium, and

e) recovering the α-amylase variant from the culture obtained in stepd).

The invention also relates to a variant (which is a variant accordingthe invention) prepared by the latter method.

In the present context, the term “simulating at least one washing and/ordishwashing condition” is intended to indicate a simulation of, e.g.,the temperature or pH prevailing during washing or dishwashing, or ofthe chemical composition of a detergent composition to be used in thewashing or dishwashing treatment. The term “chemical composition” isintended to include one, or a combination of two or more, constituentsof the detergent composition in question. The constituents of a numberof different detergent compositions are listed further below.

The “population of cells” referred to in step a) may suitably beconstructed by cloning a DNA sequence encoding a parent α-amylase andsubjecting the DNA to site-directed or random mutagenesis as describedherein.

In the present context the term “variant” is used interchangeably withthe term “mutant”. The term “variant” is intended to include hybridα-amylases, i.e. α-amylases comprising parts of at least two differentα-amylolytic enzymes. Thus, such a hybrid may be constructed, e.g.,from: one or more parts each deriving from a variant as already definedabove; or one or more parts each deriving from a variant as alreadydefined above, and one or more parts each deriving from an unmodifiedparent α-amylase. In this connection, the invention also relates to amethod of producing such a hybrid α-amylase having improved washingand/or dishwashing performance as compared to any of its constituentenzymes (i.e. as compared to any of the enzymes which contribute a partto the hybrid), which method comprises:

a) recombining in vivo or in vitro the N-terminal coding region of anα-amylase gene or corresponding cDNA of one of the constituentα-amylases with the C-terminal coding region of an α-amylase gene orcorresponding cDNA of another constituent α-amylase to formrecombinants,

b) selecting recombinants that produce a hybrid α-amylase havingimproved washing and/or dishwashing performance as compared to any ofits constituent α-amylases,

c) culturing recombinants selected in step b) under suitable conditionsin an appropriate culture medium, and

d) recovering the hybrid α-amylase from the culture obtained in step c).

In further aspects the invention relates to the use of an α-amylasevariant of the invention [including any variant or hybrid prepared byone of the above mentioned methods] as a detergent enzyme, in particularfor washing or dishwashing, to a detergent additive and a detergentcomposition comprising the α-amylase variant, and to the use of anα-amylase variant of the invention for textile desizing.

Random mutagenesis may be used to generate variants according to theinvention, and the invention further relates to a method of preparing avariant of a parent α-amylase, which method comprises

(a) subjecting a DNA sequence encoding the parent α-amylase to randommutagenesis,

(b) expressing the mutated DNA sequence obtained in step (a) in a hostcell, and

(c) screening for host cells expressing a mutated amylolytic enzymewhich has improved properties as described above (e.g. properties suchas decreased calcium dependency, increased oxidation stability,increased thermostability, and/or improved activity at relatively highpH) as compared to the parent α-amylase.

DETAILED DISCLOSURE OF THE INVENTION Nomenclature

In the present description and claims, the conventional one-letter codesfor nucleotides and the conventional one-letter and three-letter codesfor amino acid residues are used. For ease of reference, α-amylasevariants of the invention are described by use of the followingnomenclature:

Original amino acid(s):position(s):substituted amino acid(s)

According to this nomenclature, and by way of example, the substitutionof alanine for asparagine in position 30 is shown as:

-   -   Ala 30 Asn or A30N        a deletion of alanine in the same position is shown as:    -   Ala 30* or A30*        and insertion of an additional amino acid residue, such as        lysine, is shown as:    -   Ala 30 AlaLys or A30AK

A deletion of a consecutive stretch of amino acid residues, exemplifiedby amino acid residues 30-33, is indicated as (30-33)*.

Where a specific α-amylase contains a “deletion” (i.e. lacks an aminoacid residue) in comparison with other α-amylases and an insertion ismade in such a position, this is indicated as:

-   -   *36 Asp or *36D        for insertion of an aspartic acid in position 36.

Multiple mutations are separated by plus signs, i.e.:

-   -   Ala 30 Asp+Glu 34 Ser or A30N+E34S        representing mutations in positions 30 and 34 (in which alanine        and glutamic acid replace, i.e. are substituted for, asparagine        and serine, respectively).

When one or more alternative amino acid residues may be inserted in agiven position this is indicated as:

A30N,E or A30N or A30E

Furthermore, when a position suitable for modification is identifiedherein without any specific modification being suggested, it is to beunderstood that any other amino acid residue may be substituted for theamino acid residue present in that position (i.e. any amino acidresidue—other than that normally present in the position inquestion—chosen among A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T,W, Y and V). Thus, for instance, when a modification (replacement) of amethionine in position 202 is mentioned, but not specified, it is to beunderstood that any of the other amino acids may be substituted for themethionine, i.e. any other amino acid chosen amongA,R,N,D,C,Q,E,G,H,I,L,K,F,P,S,T,W,Y and V.

The Parent α-Amylase

As already indicated, an α-amylase variant of the invention is verysuitably prepared on the basis of a parent α-amylase having one of theamino acid sequences shown in SEQ ID No. 1, SEQ ID No. 2, SEQ ID No. 3and SEQ ID No. 7, respectively (vide infra).

The parent α-amylases having the amino acid sequences shown in SEQ IDNo. 1 and SEQ ID No. 2, respectively, are obtainable from alkalophilicBacillus strains (strain NCIB 12512 and strain NCIB 12513,respectively), both of which are described in detail in EP 0 277 216 B1.The preparation, purification and sequencing of these two parentα-amylases is described in WO 95/26397 [see the Experimental sectionherein (vide infra)].

The parent α-amylase having the amino acid sequence shown in SEQ ID No.3 is obtainable from Bacillus stearothermophilus and is described in,inter alia, J. Bacteriol. 166 (1986) pp. 635-643.

The parent α-amylase having the amino acid sequence shown in SEQ ID No.7 (which is the same sequence as that numbered 4 in FIG. 1) isobtainable from a “Bacillus sp. #707” and is described by Tsukamoto etal. in Biochem. Biophys. Res. Commun. 151 (1988) pp. 25-31.

Apart from variants of the above-mentioned parent α-amylases having theamino acid sequences shown in SEQ ID No. 1, SEQ ID No. 2, SEQ ID No. 3and SEQ ID No. 7, respectively, other interesting variants according tothe invention include variants of parent α-amylases which have aminoacid sequences exhibiting a high degree of homology, such as at least70% homology, preferably (as already indicated) at least 80% homology,desirably at least 85% homology, and more preferably at least 90%homology, e.g. ≧95% homology, with at least one of the latter four aminoacid sequences.

As also already indicated above, further criteria for identifying asuitable parent α-amylase are a) that the α-amylase displays animmunological cross-reaction with an antibody raised against anα-amylase having one of the amino acid sequences shown in SEQ ID No. 1,SEQ ID No. 2, SEQ ID No. 3 and SEQ ID No. 7, respectively, and/or b)that the α-amylase is encoded by a DNA sequence which hybridizes withthe same probe as a DNA sequence encoding an α-amylase having one of theamino acid sequences shown in SEQ ID No. 1, SEQ ID No. 2, SEQ ID No. 3and SEQ ID No. 7, respectively.

As already mentioned, with regard to determination of the degree ofhomology of polypeptides (such as enzymes), amino acid sequencecomparisons can be performed using known algorithms, such as the onedescribed by Lipman and Pearson (1985).

Assays for immunological cross-reactivity may be carried out using anantibody raised against, or reactive with, at least one epitope of theα-amylase having the amino acid sequence shown in SEQ ID No. 1, or ofthe α-amylase having the amino acid sequence shown in SEQ ID No. 2, orof the α-amylase having the amino acid sequence shown in SEQ ID No. 3,or of the α-amylase having the amino acid sequence shown in SEQ ID No.7.

The antibody, which may either be monoclonal or polyclonal, may beproduced by methods known in the art, e.g. as described by Hudson et al.(1989). Examples of suitable assay techniques well known in the artinclude Western Blotting and Radial Immunodiffusion Assay, e.g. asdescribed by Hudson et al. (1989).

The oligonucleotide probe for use in the identification of suitableparent α-amylases on the basis of probe hybridization [criterion b)above] may, by way of example, suitably be prepared on the basis of thefull or partial amino acid sequence of an α-amylase having one of thesequences shown in SEQ ID No. 1, SEQ ID No. 2, SEQ ID No. 3 and SEQ IDNo. 7, respectively, or on the basis of the full or partial nucleotidesequence corresponding thereto.

Suitable conditions for testing hybridization involve presoaking in5×SSC and prehybridizing for 1 h at ˜40° C. in a solution of 20%formamide, 5×Denhardt's solution, 50 mM sodium phosphate, pH 6.8, and 50μg of denatured sonicated calf thymus DNA, followed by hybridization inthe same solution supplemented with 100 μM ATP for 18 h at ±40° C., orusing other methods described by, e.g., Sambrook et al. (1989).

Influence of Mutations on Particular Properties

From the results obtained by the present inventors it appears thatchanges in a particular property, e.g. thermal stability or oxidationstability, exhibited by a variant relative to the parent α-amylase inquestion can to a considerable extent be correlated with the type of,and positioning of, mutation(s) (amino acid substitutions, deletions orinsertions) in the variant. It is to be understood, however, that theobservation that a particular mutation or pattern of mutations leads tochanges in a given property in no way excludes the possibility that themutation(s) in question can also influence other properties.

Oxidation stability: With respect to increasing the oxidation stabilityof an α-amylase variant relative to its parent α-amylase, it appears tobe particularly desirable that at least one, and preferably multiple,oxidizable amino acid residue(s) of the parent has/have been deleted orreplaced (i.e. substituted by) a different amino acid residue which isless susceptible to oxidation than the original oxidizable amino acidresidue.

Particularly relevant oxidizable amino acid residues in this connectionare cysteine, methionine, tryptophan and tyrosine. Thus, for example, inthe case of parent α-amylases containing cysteine it is anticipated thatdeletion of cysteine residues, or substitution thereof by lessoxidizable amino acid residues, will be of importance in obtainingvariants with improved oxidation stability relative to the parentα-amylase.

In the case of the above-mentioned parent α-amylases having the aminoacid sequences shown in SEQ ID No. 1, SEQ ID No. 2 and SEQ ID No. 7,respectively, all of which contain no cysteine residues but have asignificant methionine content, the deletion or substitution ofmethionine residues is particularly relevant with respect to achievingimproved oxidation stability of the resulting variants. Thus, deletionor substitution [e.g. by threonine (T), or by one of the other aminoacids listed above] of one or more of the methionine residues inpositions M9, M10, M105, M202, M208, M261, M309, M382, M430 and M440 ofthe amino acid sequences shown in SEQ ID No. 1, SEQ ID No. 2 and SEQ IDNo. 7, and/or in position M323 of the amino acid sequence shown in SEQID No. 2 (or deletion or substitution of methionine residues inequivalent positions in the sequence of another α-amylase meeting one ofthe other criteria for a parent α-amylase mentioned above) appear to beparticularly effective with respect to increasing the oxidationstability.

In the case of the parent α-amylase having the amino acid sequence shownin SEQ ID No. 3, relevant amino acid residues which may be deleted orsubstituted with a view to improving the oxidation stability include thesingle cysteine residue (C363) and—by analogy with the sequences shownin SEQ ID No. 1 and SEQ ID No. 3—the methionine residues located inpositions M8, M9, M96, M200, M206, M284, M307, M311, M316 and M438.

In this connection, the term “equivalent position” denotes a positionwhich, on the basis of an alignment of the amino acid sequence of theparent α-amylase in question with the “reference” α-amylase amino acidsequence in question (for example the sequence shown in SEQ ID No. 1) soas to achieve juxtapositioning of amino acid residues/regions which arecommon to both, corresponds most closely to (e.g. is occupied by thesame amino acid residue as) a particular position in the referencesequence in question.

Particularly interesting mutations in connection with modification(improvement) of the oxidation stability of the α-amylases having theamino acid sequences shown in SEQ ID No. 1, SEQ ID No. 2 and SEQ ID No.7, respectively, are one or more of the following methioninesubstitutions (or equivalents thereof in the amino acid sequences ofother α-amylases meeting the requirements of a parent α-amylase in thecontext of the invention): M202A,R,N,D,Q,E,G,H,I,L,K,F,P,S,T,W,Y,V.

Further relevant methionine substitutions in the amino acid sequenceshown in SEQ ID No. 2 are: M323A,R,N,D,Q,E,G,H,I,L,K,F,P,S,T,W,Y,V.

Particularly interesting mutations in connection with modification(improvement) of the oxidation stability of the α-amylase having theamino acid sequence shown in SEQ ID No. 3 are one or more of thefollowing methionine substitutions:M200A,R,N,D,Q,E,G,H,I,L,K,F,P,S,T,W,Y,V;M311A,R,N,D,Q,E,G,H,I,L,K,F,P,S,T,W,Y,V; andM316A,R,N,D,Q,E,G,H,I,L,K,F,P,S,T,W,Y,V.

Thermal stability: With respect to increasing the thermal stability ofan α-amylase variant relative to its parent α-amylase, it appears to beparticularly desirable to delete at least one, and preferably two oreven three, of the following amino acid residues in the amino acidsequence shown in SEQ ID No. 1 (or their equivalents): F180, R181, G182,T183, G184 and K185. The corresponding, particularly relevant (andequivalent) amino acid residues in the amino acid sequences shown in SEQID No. 2, SEQ ID No. 3 and SEQ ID No. 7, respectively, are: F180, R181,G182, D183, G184 and K185 (SEQ ID No. 2); F178, R179, G180, I181, G182and K183 (SEQ ID No. 3); and F180, R181, G182, H183, G184 and K185 (SEQID No. 7).

Particularly interesting pairwise deletions of this type are as follows:R181*+G182*; and T183*+G184* (SEQ ID No. 1); R181*+G182*; andD183*+G184* (SEQ ID No. 2); R179*+G180*; and I181*+G182* (SEQ ID No. 3);and R181*+G182*; and H183*+G184* (SEQ ID No. 7)

(or equivalents of these pairwise deletions in another α-amylase meetingthe requirements of a parent α-amylase in the context of the presentinvention).

Other mutations which appear to be of importance in connection withthermal stability are substitutions of one or more of the amino acidresidues from P260 to I275 in the sequence shown in SEQ ID No. 1 (orequivalents thereof in another parent α-amylase in the context of theinvention), such as substitution of the lysine residue in position 269.

Examples of specific mutations which appear to be of importance inconnection with the thermal stability of an α-amylase variant relativeto the parent α-amylase in question are one or more of the followingsubstitutions in the amino acid sequence shown in SEQ ID No. 1 (orequivalents thereof in another parent α-amylase in the context of theinvention): K269R; P260E; R124P; M105F,I,L,V; M208F,W,Y; L2171;V206I,L,F.

For the parent α-amylase having the amino acid sequence shown in SEQ IDNo. 2, important further (equivalent) mutations are, correspondingly,one or more of the substitutions: M105F,I,L,V; M208F,W,Y; L217I;V206I,L,F; and K269R.

For the parent α-amylase having the amino acid sequence shown in SEQ IDNo. 3, important further (equivalent) mutations are, correspondingly,one or both of the substitutions: M206F,W,Y; and L215I.

For the parent α-amylase having the amino acid sequence shown in SEQ IDNo. 7, important further (equivalent) mutations are, correspondingly,one or more of the substitutions: M105F,I,L,V; M208F,W,Y; L217I; andK269R.

Still further examples of mutations which appear to be of importance,inter alia, in achieving improved thermal stability of an α-amylasevariant relative to the parent α-amylase in question are one or more ofthe following substitutions in the amino acid sequences shown in SEQ IDNo. 1, SEQ ID No. 2 and SEQ ID No. 7 (or equivalents thereof in anotherparent α-amylase in the context of the invention): A354C+V479C;L351C+M430C; N457D,E+K385R; L355D,E+M430R,K; L355D,E+I411R,K; andN457D,E.

Ca²⁺ dependency: With respect to achieving decreased Ca²⁺ dependency ofan α-amylase variant relative to its parent α-amylase [i.e. with respectto obtaining a variant which exhibits satisfactory amylolytic activityin the presence of a lower concentration of calcium ion in theextraneous medium than is necessary for the parent enzyme, and which,for example, therefore is less sensitive than the parent to calciumion-depleting conditions such as those obtaining in media containingcalcium-complexing agents (such as certain detergent builders)], itappears to be particularly desirable to incorporate one or more of thefollowing substitutions in the amino acid sequences shown in SEQ ID No.1, SEQ ID No. 2 and SEQ ID No. 7 (or an equivalent substitution inanother parent α-amylase in the context of the invention): Y243F, K108R,K179R, K239R, K242R, K269R, D163N, D188N, D192N, D199N, D205N, D207N,D209N, E190Q, E194Q and N106D.

In the case of the amino acid sequence shown in SEQ ID No. 3,particularly desirable substitutions appear, correspondingly(equivalently), to be one or more of the following: K107R, K177R, K237R,K240R, D162N, D186N, D190N, D197N, D203N, D205N, D207N, E188Q and E192Q.

As well as the above-mentioned replacements of D residues with Nresidues, or of E residues with Q residues, other relevant substitutionsin the context of reducing Ca²⁺ dependency are replacement of the Dand/or E residues in question with any other amino acid residue.

Further substitutions which appear to be of importance in the context ofachieving reduced Ca²⁺ dependency are pairwise substitutions of theamino acid residues present at: positions 113 and 151, and positions 351and 430, in the amino acid sequences shown in SEQ ID No. 1, SEQ ID No. 2and SEQ ID No. 7; and at: positions 112 and 150, and positions 349 and428, in the amino acid sequence shown in SEQ ID No. 3 (or equivalentpairwise substitutions in another parent α-amylase in the context of theinvention), i.e. pairwise substitutions of the following amino acidresidues:

G113+N151 (in relation to SEQ ID No. 1); A113+T151 (in relation to SEQID No. 2 and SEQ ID No. 7); and G112+T150 (in relation to SEQ ID No. 3);and

L351+M430 (in relation to SEQ ID No. 1, SEQ ID No. 2 and SEQ ID No. 7);and L349+I428 (in relation to SEQ ID No. 3).

Particularly interesting pairwise substitutions of this type withrespect to achieving decreased Ca²⁺ dependency are the following:

G113T+N151I (in relation to SEQ ID No. 1); A113T+T151I (in relation toSEQ ID No. 2 and SEQ ID No. 7); and G112T+T150I (in relation to SEQ IDNo. 3); and L351C+M430C (in relation to SEQ ID No. 1, SEQ ID No. 2 andSEQ ID No. 7); and L349C+I428C (in relation to SEQ ID No. 3).

In connection with substitutions of relevance for Ca²⁺ dependency, someother substitutions which appear to be of importance in stabilizing theenzyme conformation, and which it is contemplated may achieve this by,e.g., enhancing the strength of binding or retention of calcium ion ator within a calcium binding site within the α-amylolytic enzyme, are oneor more of the following substitutions in the amino acid sequences shownin SEQ ID No. 1, SEQ ID No. 2 and SEQ ID No. 7 (or an equivalentsubstitution in another parent α-amylase in the context of theinvention): G304W,F,Y,R,I,L,V,Q,N; G305A,S,N,D,Q,E,R,K; and H408Q,E.

Corresponding (equivalent) substitutions in the amino acid sequenceshown in SEQ ID No. 3 are: G302W,F,Y,R,I,L,V,Q,N; andG303A,S,N,D,Q,E,R,K.

Further mutations which appear to be of importance in the context ofachieving reduced Ca²⁺ dependency are pairwise deletions of amino acids(i.e. deletion of two amino acids) at positions selected among R181,G182, T183 and G184 in the amino acid sequence shown in SEQ ID No. 1 (orequivalent positions in the amino acid sequence of another α-amylasemeeting the requirements of a parent α-amylase in the context of theinvention).Such pairwise deletions are thus the following:

R181*+G182*; T183*+G184*; R181*+T183*; G182*+T183*; G182*+G184*; andR181*+G184* (SEQ ID No. 1);

R181*+G182*; D183*+G184*; R181*+D183*; G182*+D183*; G182*+G184*; andR181*+G184* (SEQ ID No. 2);

R179*+G180*; I181*+G182*; R179*+I181*; G180*+I181*; G180*+G182*; andR179*+G182* (SEQ ID No. 3); and

R181*+G182*; H183*+G184*; R181*+H183*; G182*+H183*; G182*+G184*; andR181*+G184* (SEQ ID No. 7);

(or equivalents of these pairwise deletions in another α-amylase meetingthe requirements of a parent α-amylase in the context of the presentinvention).

Isoelectric point (pI): Preliminary results indicate that the washingperformance, e.g. the laundry washing performance, of an α-amylase isoptimal when the pH of the washing liquor (washing medium) is close tothe pI value for the α-amylase in question. It will thus be desirable,where appropriate, to produce an α-amylase variant having an isoelectricpoint (pI value) which is better matched to the pH of a medium (such asa washing medium) in which the enzyme is to be employed than theisoelectric point of the parent α-amylase in question.

With respect to decreasing the isoelectric point, preferred mutations inthe amino acid sequence shown in SEQ ID No. 1 include one or more of thefollowing substitutions: Q86E, R124P, S154D, T183D, V222E, P260E, R310A,Q346E, Q391E, N437E, K444Q and R452H. Appropriate combinations of thesesubstitutions in the context of decreasing the isoelectric pointinclude: Q391E+K444Q; and Q391E+K444Q+S154D.

Correspondingly, preferred mutations in the amino acid sequence shown inSEQ ID No. 3 with respect to decreasing the isoelectric point includeone or more of the substitutions: L85E, S153D, 1181D, K220E, P258E,R308A, P344E, Q358E and S435E.

With respect to increasing the isoelectric point, preferred mutations inthe amino acid sequence shown in SEQ ID No. 2 include one or more of thefollowing substitutions: E86Q,L; D154S; D183T,I; E222V,K; E260P; A310R;E346Q,P; E437N,S; and H452R.

In the Experimental section below, the construction of a number ofvariants according to the invention is described.

α-Amylase variants of the invention will, apart from having one or moreimproved properties as discussed above, preferably be such that theyhave a higher starch hydrolysis velocity at low substrate concentrationsthan the parent α-amylase. Alternatively, an α-amylase variant of theinvention will preferably be one which has a higher V_(max) and/or alower K_(m) than the parent α-amylase when tested under the sameconditions. In the case of a hybrid α-amylase, the “parent α-amylase” tobe used for the comparison should be the one of the constituent enzymeshaving the best performance.

V_(max) and K_(m) (parameters of the Michaelis-Menten equation) may bedetermined by well-known procedures.

Methods of Preparing α-Amylase Variants

Several methods for introducing mutations into genes are known in theart. After a brief discussion of the cloning of α-amylase-encoding DNAsequences, methods for generating mutations at specific sites within theα-amylase-encoding sequence will be discussed.

Cloning a DNA Sequence Encoding an α-Amylase

The DNA sequence encoding a parent α-amylase may be isolated from anycell or microorganism producing the α-amylase in question, using variousmethods well known in the art. First, a genomic DNA and/or cDNA libraryshould be constructed using chromosomal DNA or messenger RNA from theorganism that produces the α-amylase to be studied. Then, if the aminoacid sequence of the α-amylase is known, homologous, labelledoligonucleotide probes may be synthesized and used to identifyα-amylase-encoding clones from a genomic library prepared from theorganism in question. Alternatively, a labelled oligonucleotide probecontaining sequences homologous to a known α-amylase gene could be usedas a probe to identify α-amylase-encoding clones, using hybridizationand washing conditions of lower stringency.

Yet another method for identifying α-amylase-encoding clones wouldinvolve inserting fragments of genomic DNA into an expression vector,such as a plasmid, transforming α-amylase-negative bacteria with theresulting genomic DNA library, and then plating the transformed bacteriaonto agar containing a substrate for α-amylase, thereby allowing clonesexpressing the α-amylase to be identified.

Alternatively, the DNA sequence encoding the enzyme may be preparedsynthetically by established standard methods, e.g. the phosphoamiditemethod described by S. L. Beaucage and M. H. Caruthers (1981) or themethod described by Matthes et al. (1984). In the phosphoamidite method,oligonucleotides are synthesized, e.g. in an automatic DNA synthesizer,purified, annealed, ligated and cloned in appropriate vectors.

Finally, the DNA sequence may be of mixed genomic and synthetic origin,mixed synthetic and cDNA origin or mixed genomic and cDNA origin,prepared by ligating fragments of synthetic, genomic or cDNA origin (asappropriate, the fragments corresponding to various parts of the entireDNA sequence), in accordance with standard techniques. The DNA sequencemay also be prepared by polymerase chain reaction (PCR) using specificprimers, for instance as described in U.S. Pat. No. 4,683,202 or R. K.Saiki et al. (1988).

Site-Directed Mutagenesis

Once an α-amylase-encoding DNA sequence has been isolated, and desirablesites for mutation identified, mutations may be introduced usingsynthetic oligonucleotides. These oligonucleotides contain nucleotidesequences flanking the desired mutation sites; mutant nucleotides areinserted during oligonucleotide synthesis. In a specific method, asingle-stranded gap of DNA, bridging the α-amylase-encoding sequence, iscreated in a vector carrying the α-amylase gene. Then the syntheticnucleotide, bearing the desired mutation, is annealed to a homologousportion of the single-stranded DNA. The remaining gap is then filled inwith DNA polymerase I (Klenow fragment) and the construct is ligatedusing T4 ligase. A specific example of this method is described inMorinaga et al. (1984). U.S. Pat. No. 4,760,025 discloses theintroduction of oligonucleotides encoding multiple mutations byperforming minor alterations of the cassette. However, an even greatervariety of mutations can be introduced at any one time by the Morinagamethod, because a multitude of oligonucleotides, of various lengths, canbe introduced.

Another method of introducing mutations into α-amylase-encoding DNAsequences is described in Nelson and Long (1989). It involves the 3-stepgeneration of a PCR fragment containing the desired mutation introducedby using a chemically synthesized DNA strand as one of the primers inthe PCR reactions. From the PCR-generated fragment, a DNA fragmentcarrying the mutation may be isolated by cleavage with restrictionendonucleases and reinserted into an expression plasmid.

Random Mutagenesis

Random mutagenesis is suitably performed either as localized orregion-specific random mutagenesis in at least three parts of the genetranslating to the amino acid sequence shown in question, or within thewhole gene.

For region-specific random mutagenesis with a view to improving thethermal stability, the following codon positions, in particular, mayappropriately be targeted (using one-letter amino acid abbreviations andthe numbering of the amino acid residues in the sequence in question):

In the Amino Acid Sequence Shown in SEQ ID No. 1:

120-140 = VEVNRSNRNQETSGEYAIEAW 178-187 = YKFRGTGKAW 264-277= VAEFWKNDLGAIEN

In the Amino Acid Sequence Shown in SEQ ID No. 2:

120-140 = VEVNPNNRNQEISGDYTIEAW 178-187 = YKFRGDGKAW 264-277= VAEFWKNDLGALEN

In the Amino Acid Sequence Shown in SEQ ID No. 3:

119-139 = VEVNPSDRNQEISGTYQIQAW 176-185 = YKFRGIGKAW 262-275= VGEYWSYDINKLHN

In the Amino Acid Sequence Shown in SEQ ID No. 7:

120-140 = VEVNPNNRNQEVTGEYTIEAW 178-187 = YKFRGHGKAW 264-277= VAEFWKNDLGAIEN

With a view to achieving reduced Ca²⁺ dependency, the following codonpositions, in particular, may appropriately be targeted:

In the Amino Acid Sequence Shown in SEQ ID No. 1:

178-209 = YKFRGTGKAWDWEVDTENGNYDYLMYADVDMD 237-246 = AVKHIKYSFT

In the Amino Acid Sequence Shown in SEQ ID No. 2:

178-209 = YKFRGDGKAWDWEVDSENGNYDYLMYADVDMD 237-246 = AVKHIKYSFT

In the Amino Acid Sequence Shown in SEQ ID No. 7:

178-209 = YKFRGHGKAWDWEVDTENGNYDYLMYADIDMD 237-246 = AVKHIKYSFT

With a view to achieving improved binding of a substrate (i.e. improvedbinding of a carbohydrate species—such as amylose or amylopectin—whichis a substrate for α-amylolytic enzymes) by an α-amylase variant,modified (e.g. higher) substrate specificity and/or modified (e.g.higher) specificity with respect to cleavage (hydrolysis) of substrate,it appears that the following codon positions for the amino acidsequence shown in SEQ ID No. 1 (or equivalent codon positions foranother parent α-amylase in the context of the invention) mayparticularly appropriately be targeted:

In the amino acid sequence shown in SEQ ID No. 1:

 15-20 = WYLPND  52-58 = SQNDVGY  72-78 = KGTVRTK 104-111 = VMNHKGGA165-174 = TDWDQSRQLQ 194-204 = ENGNYDYLMYA 234-240 = RIDAVKH 332-340= HDSQPGEAL

The random mutagenesis of a DNA sequence encoding a parent α-amylase tobe performed in accordance with step a) of the above-described method ofthe invention may conveniently be performed by use of any method knownin the art.

For instance, the random mutagenesis may be performed by use of asuitable physical or chemical mutagenizing agent, by use of a suitableoligonucleotide, or by subjecting the DNA sequence to PCR generatedmutagenesis. Furthermore, the random mutagenesis may be performed by useof any combination of these mutagenizing agents.

The mutagenizing agent may, e.g., be one which induces transitions,transversions, inversions, scrambling, deletions, and/or insertions.

Examples of a physical or chemical mutagenizing agent suitable for thepresent purpose include ultraviolet (UV) irradiation, hydroxylamine,N-methyl-N′-nitro-N-nitrosoguanidine (MNNG), O-methyl hydroxylamine,nitrous acid, ethyl methane sulphonate (EMS), sodium bisulphite, formicacid, and nucleotide analogues.

When such agents are used, the mutagenesis is typically performed byincubating the DNA sequence encoding the parent enzyme to be mutagenizedin the presence of the mutagenizing agent of choice under suitableconditions for the mutagenesis to take place, and selecting for mutatedDNA having the desired properties.

When the mutagenesis is performed by the use of an oligonucleotide, theoligonucleotide may be doped or spiked with the three non-parentnucleotides during the synthesis of the oligonucleotide at the positionswhich are to be changed. The doping or spiking may be done so thatcodons for unwanted amino acids are avoided. The doped or spikedoligonucleotide can be incorporated into the DNA encoding the amylolyticenzyme by any published technique, using e.g. PCR, LCR or any DNApolymerase and ligase.

When PCR-generated mutagenesis is used, either a chemically treated ornon-treated gene encoding a parent α-amylase enzyme is subjected to PCRunder conditions that increase the misincorporation of nucleotides(Deshler 1992; Leung et al., Technique, Vol. 1, 1989, pp. 11-15).

A mutator strain of E. coli (Fowler et al., Molec. Gen. Genet, 133,1974, pp. 179-191), S. cereviseae or any other microbial organism may beused for the random mutagenesis of the DNA encoding the amylolyticenzyme by e.g. transforming a plasmid containing the parent enzyme intothe mutator strain, growing the mutator strain with the plasmid andisolating the mutated plasmid from the mutator strain. The mutatedplasmid may subsequently be transformed into the expression organism.

The DNA sequence to be mutagenized may conveniently be present in agenomic or cDNA library prepared from an organism expressing the parentamylolytic enzyme. Alternatively, the DNA sequence may be present on asuitable vector such as a plasmid or a bacteriophage, which as such maybe incubated with or otherwise exposed to the mutagenizing agent. TheDNA to be mutagenized may also be present in a host cell either by beingintegrated in the genome of said cell or by being present on a vectorharbored in the cell. Finally, the DNA to be mutagenized may be inisolated form. It will be understood that the DNA sequence to besubjected to random mutagenesis is preferably a cDNA or a genomic DNAsequence.

In some cases it may be convenient to amplify the mutated DNA sequenceprior to the expression step (b) or the screening step (c) beingperformed. Such amplification may be performed in accordance withmethods known in the art, the presently preferred method beingPCR-generated amplification using oligonucleotide primers prepared onthe basis of the DNA or amino acid sequence of the parent enzyme.

Subsequent to the incubation with or exposure to the mutagenizing agent,the mutated DNA is expressed by culturing a suitable host cell carryingthe DNA sequence under conditions allowing expression to take place. Thehost cell used for this purpose may be one which has been transformedwith the mutated DNA sequence, optionally present on a vector, or onewhich was carried the DNA sequence encoding the parent enzyme during themutagenesis treatment. Examples of suitable host cells are thefollowing: gram positive bacteria such as Bacillus subtilis, Bacilluslicheniformis, Bacillus lentus, Bacillus brevis, Bacillusstearothermophilus, Bacillus alkalophilus, Bacillus amyloliquefaciens,Bacillus coagulans, Bacillus circulans, Bacillus lautus, Bacillusmegaterium, Bacillus thuringiensis, Streptomyces lividans orStreptomyces murinus; and gram negative bacteria such as E. coli.

The mutated DNA sequence may further comprise a DNA sequence encodingfunctions permitting expression of the mutated DNA sequence.

Localized random mutagenesis: the random mutagenesis may advantageouslybe localized to a part of the parent α-amylase in question. This may,e.g., be advantageous when certain regions of the enzyme have beenidentified to be of particular importance for a given property of theenzyme, and when modified are expected to result in a variant havingimproved properties. Such regions may normally be identified when thetertiary structure of the parent enzyme has been elucidated and relatedto the function of the enzyme.

The localized random mutagenesis is conveniently performed by use ofPCR-generated mutagenesis techniques as described above or any othersuitable technique known in the art.

Alternatively, the DNA sequence encoding the part of the DNA sequence tobe modified may be isolated, e.g. by being inserted into a suitablevector, and said part may subsequently be subjected to mutagenesis byuse of any of the mutagenesis methods discussed above.

With respect to the screening step in the above-mentioned method of theinvention, this may conveniently performed by use of a filter assaybased on the following principle:

A microorganism capable of expressing the mutated amylolytic enzyme ofinterest is incubated on a suitable medium and under suitable conditionsfor the enzyme to be secreted, the medium being provided with a doublefilter comprising a first protein-binding filter and on top of that asecond filter exhibiting a low protein binding capability. Themicroorganism is located on the second filter. Subsequent to theincubation, the first filter comprising enzymes secreted from themicroorganisms is separated from the second filter comprising themicroorganisms. The first filter is subjected to screening for thedesired enzymatic activity and the corresponding microbial coloniespresent on the second filter are identified.

The filter used for binding the enzymatic activity may be any proteinbinding filter e.g. nylon or nitrocellulose. The top filter carrying thecolonies of the expression organism may be any filter that has no or lowaffinity for binding proteins e.g. cellulose acetate or Durapore™. Thefilter may be pretreated with any of the conditions to be used forscreening or may be treated during the detection of enzymatic activity.

The enzymatic activity may be detected by a dye, fluorescence,precipitation, pH indicator, IR-absorbance or any other known techniquefor detection of enzymatic activity.

The detecting compound may be immobilized by any immobilizing agent e.g.agarose, agar, gelatine, polyacrylamide, starch, filter paper, cloth; orany combination of immobilizing agents.

α-Amylase activity is detected by Cibacron Red labelled amylopectin,which is immobilized on agarose. For screening for variants withincreased thermal and high-pH stability, the filter with bound α-amylasevariants is incubated in a buffer at pH 10.5 and 60° or 65° C. for aspecified time, rinsed briefly in deionized water and placed on theamylopectin-agarose matrix for activity detection. Residual activity isseen as lysis of Cibacron Red by amylopectin degradation. The conditionsare chosen to be such that activity due to the α-amylase having theamino acid sequence shown in SEQ ID No. 1 can barely be detected.Stabilized variants show, under the same conditions, increased colorintensity due to increased liberation of Cibacron Red.

For screening for variants with an activity optimum at a lowertemperature and/or over a broader temperature range, the filter withbound variants is placed directly on the amylopectin-Cibacron Redsubstrate plate and incubated at the desired temperature (e.g. 4° C.,10° C. or 30° C.) for a specified time. After this time activity due tothe α-amylase having the amino acid sequence shown in SEQ ID No. 1 canbarely be detected, whereas variants with optimum activity at a lowertemperature will show increase amylopectin lysis. Prior to incubationonto the amylopectin matrix, incubation in all kinds of desiredmedia—e.g. solutions containing Ca²⁺, detergents, EDTA or other relevantadditives—can be carried out in order to screen for changed dependencyor for reaction of the variants in question with such additives.

Methods of Preparing Hybrid α-Amylases

As an alternative to site-specific mutagenesis, α-amylase variants whichare hybrids of at least two constituent α-amylases may be prepared bycombining the relevant parts of the respective genes in question.

Naturally occurring enzymes may be genetically modified by random orsite directed mutagenesis as described above. Alternatively, part of oneenzyme may be replaced by a part of another to obtain a chimeric enzyme.This replacement can be achieved either by conventional in vitro genesplicing techniques or by in vivo recombination or by combinations ofboth techniques. When using conventional in vitro gene splicingtechniques, a desired portion of the α-amylase gene coding sequence maybe deleted using appropriate site-specific restriction enzymes; thedeleted portion of the coding sequence may then be replaced by theinsertion of a desired portion of a different α-amylase coding sequenceso that a chimeric nucleotide sequence encoding a new α-amylase isproduced. Alternatively, α-amylase genes may be fused, e.g. by use ofthe PCR overlay extension method described by Higuchi et al. 1988.

The in vivo recombination techniques depend on the fact that differentDNA segments with highly homologous regions (identity of DNA sequence)may recombine, i.e. break and exchange DNA, and establish new bonds inthe homologous regions. Accordingly, when the coding sequences for twodifferent but homologous amylase enzymes are used to transform a hostcell, recombination of homologous sequences in vivo will result in theproduction of chimeric gene sequences. Translation of these codingsequences by the host cell will result in production of a chimericamylase gene product. Specific in vivo recombination techniques aredescribed in U.S. Pat. No. 5,093,257 and EP 252 666.

Alternatively, the hybrid enzyme may be synthesized by standard chemicalmethods known in the art. For example, see Hunkapiller et al. (1984).Accordingly, peptides having the appropriate amino acid sequences may besynthesized in whole or in part and joined to form hybrid enzymes(variants) of the invention.

Expression of α-Amylase Variants

According to the invention, a mutated α-amylase-encoding DNA sequenceproduced by methods described above, or by any alternative methods knownin the art, can be expressed, in enzyme form, using an expression vectorwhich typically includes control sequences encoding a promoter,operator, ribosome binding site, translation initiation signal, and,optionally, a repressor gene or various activator genes.

The recombinant expression vector carrying the DNA sequence encoding anα-amylase variant of the invention may be any vector which mayconveniently be subjected to recombinant DNA procedures, and the choiceof vector will often depend on the host cell into which it is to beintroduced. Thus, the vector may be an autonomously replicating vector,i.e. a vector which exists as an extrachromosomal entity, thereplication of which is independent of chromosomal replication, e.g. aplasmid, a bacteriophage or an extrachromosomal element, minichromosomeor an artificial chromosome. Alternatively, the vector may be one which,when introduced into a host cell, is integrated into the host cellgenome and replicated together with the chromosome(s) into which it hasbeen integrated.

In the vector, the DNA sequence should be operably connected to asuitable promoter sequence. The promoter may be any DNA sequence whichshows transcriptional activity in the host cell of choice and may bederived from genes encoding proteins either homologous or heterologousto the host cell. Examples of suitable promoters for directing thetranscription of the DNA sequence encoding an α-amylase variant of theinvention, especially in a bacterial host, are the promoter of the lacoperon of E. coli, the Streptomyces coelicolor agarase gene dagApromoters, the promoters of the Bacillus licheniformis α-amylase gene(amyL), the promoters of the Bacillus stearothermophilus maltogenicamylase gene (amyM), the promoters of the Bacillus Amyloliquefaciensα-amylase (amyQ), the promoters of the Bacillus subtilis xylA and xylBgenes etc. For transcription in a fungal host, examples of usefulpromoters are those derived from the gene encoding A. oryzae TAKAamylase, Rhizomucor miehei aspartic proteinase, A. niger neutralα-amylase, A. niger acid stable α-amylase, A. niger glucoamylase,Rhizomucor miehei lipase, A. oryzae alkaline protease, A. oryzae triosephosphate isomerase or A. nidulans acetamidase.

The expression vector of the invention may also comprise a suitabletranscription terminator and, in eukaryotes, polyadenylation sequencesoperably connected to the DNA sequence encoding the α-amylase variant ofthe invention. Termination and polyadenylation sequences may suitably bederived from the same sources as the promoter.

The vector may further comprise a DNA sequence enabling the vector toreplicate in the host cell in question. Examples of such sequences arethe origins of replication of plasmids pUC19, pACYC177, pUB110, pE194,pAMB1 and pIJ702.

The vector may also comprise a selectable marker, e.g. a gene theproduct of which complements a defect in the host cell, such as the dalgenes from B. subtilis or B. licheniformis, or one which confersantibiotic resistance such as ampicillin, kanamycin, chloramphenicol ortetracyclin resistance. Furthermore, the vector may comprise Aspergillusselection markers such as amdS, argB, niaD and sC, a marker giving riseto hygromycin resistance, or the selection may be accomplished byco-transformation, e.g. as described in WO 91/17243.

While intracellular expression may be advantageous in some respects,e.g. when using certain bacteria as host cells, it is generallypreferred that the expression is extracellular.

Procedures suitable for constructing vectors of the invention encodingan α-amylase variant, and containing the promoter, terminator and otherelements, respectively, are well known to persons skilled in the art[cf., for instance, Sambrook et al. (1989)].

The cell of the invention, either comprising a DNA construct or anexpression vector of the invention as defined above, is advantageouslyused as a host cell in the recombinant production of an α-amylasevariant of the invention. The cell may be transformed with the DNAconstruct of the invention encoding the variant, conveniently byintegrating the DNA construct (in one or more copies) in the hostchromosome. This integration is generally considered to be an advantageas the DNA sequence is more likely to be stably maintained in the cell.Integration of the DNA constructs into the host chromosome may beperformed according to conventional methods, e.g. by homologous orheterologous recombination. Alternatively, the cell may be transformedwith an expression vector as described above in connection with thedifferent types of host cells.

The cell of the invention may be a cell of a higher organism such as amammal or an insect, but is preferably a microbial cell, e.g. abacterial or a fungal (including yeast) cell.

Examples of suitable bacteria are gram positive bacteria such asBacillus subtilis, Bacillus licheniformis, Bacillus lentus, Bacillusbrevis, Bacillus stearothermophilus, Bacillus alkalophilus, Bacillusamyloliquefaciens, Bacillus coagulans, Bacillus circulars, Bacilluslautus, Bacillus megaterium, Bacillus thuringiensis, or Streptomyceslividans or Streptomyces murinus, or gram negative bacteria such as E.coli. The transformation of the bacteria may, for instance, be effectedby protoplast transformation or by using competent cells in a mannerknown per se.

The yeast organism may favorably be selected from a species ofSaccharomyces or Schizosaccharomyces, e.g. Saccharomyces cerevisiae. Thefilamentous fungus may advantageously belong to a species ofAspergillus, e.g. Aspergillus oryzae or Aspergillus niger. Fungal cellsmay be transformed by a process involving protoplast formation andtransformation of the protoplasts followed by regeneration of the cellwall in a manner known per se. A suitable procedure for transformationof Aspergillus host cells is described in EP 238 023.

In a yet further aspect, the present invention relates to a method ofproducing an α-amylase variant of the invention, which method comprisescultivating a host cell as described above under conditions conducive tothe production of the variant and recovering the variant from the cellsand/or culture medium.

The medium used to cultivate the cells may be any conventional mediumsuitable for growing the host cell in question and obtaining expressionof the α-amylase variant of the invention. Suitable media are availablefrom commercial suppliers or may be prepared according to publishedrecipes (e.g. as described in catalogues of the American Type CultureCollection).

The α-amylase variant secreted from the host cells may conveniently berecovered from the culture medium by well-known procedures, includingseparating the cells from the medium by centrifugation or filtration,and precipitating proteinaceous components of the medium by means of asalt such as ammonium sulphate, followed by the use of chromatographicprocedures such as ion exchange chromatography, affinity chromatography,or the like.

INDUSTRIAL APPLICATIONS

Owing to their activity at alkaline pH values, α-amylase variants of theinvention are well suited for use in a variety of industrial processes.In particular, they find potential applications as a component inwashing, dishwashing and hard surface cleaning detergent compositions(vide infra), but may also be useful in the production of sweeteners andethanol from starch. Conditions for conventional starch-convertingprocesses and liquefaction and/or saccharification processes aredescribed in, for instance, U.S. Pat. No. 3,912,590, EP 252,730 and EP63,909.

Some areas of application of α-amylase variants of the invention areoutlined below.

Paper-related applications: α-Amylase variants of the invention possessproperties of value in the production of lignocellulosic materials, suchas pulp, paper and cardboard, from starch-reinforced waste paper andwaste cardboard, especially where repulping occurs at a pH above 7, andwhere amylases can facilitate the disintegration of the waste materialthrough degradation of the reinforcing starch.

α-Amylase variants of the invention are well suited for use in thedeinking/recycling processes of making paper out of starch-coated orstarch-containing waste printed paper. It is usually desirable to removethe printing ink in order to produce new paper of high brightness;examples of how the variants of the invention may be used in this wayare described in PCT/DK94/00437.

α-Amylase variants of the invention may also be very useful in modifyingstarch where enzymatically modified starch is used in papermakingtogether with alkaline fillers such as calcium carbonate, kaolin andclays. With alkaline α-amylase variants of the invention it is feasibleto modify the starch in the presence of the filler, thus allowing for asimpler, integrated process.

Textile desizing: α-Amylase variants of the invention are also wellsuited for use in textile desizing. In the textile processing industry,α-amylases are traditionally used as auxiliaries in the desizing processto facilitate the removal of starch-containing size which has served asa protective coating on weft yarns during weaving.

Complete removal of the size coating after weaving is important toensure optimum results in subsequent processes in which the fabric isscoured, bleached and dyed. Enzymatic starch degradation is preferredbecause it does not harm the fibers of the textile or fabric.

In order to reduce processing costs and increase mill throughput, thedesizing processing is sometimes combined with the scouring andbleaching steps. In such cases, non-enzymatic auxiliaries such as alkalior oxidation agents are typically used to break down the starch, becausetraditional α-amylases are not very compatible with high pH levels andbleaching agents. The non-enzymatic breakdown of the starch size doeslead to some fibre damage because of the rather aggressive chemicalsused.

α-Amylase variants of the invention exhibiting improved starch-degradingperformance at relatively high pH levels and in the presence ofoxidizing (bleaching) agents are thus well suited for use in desizingprocesses as described above, in particular for replacement ofnon-enzymatic desizing agents currently used. The α-amylase variant maybe used alone, or in combination with a cellulase when desizingcellulose-containing fabric or textile.

Beer production: α-Amylase variants of the invention are also believedto be very useful in beer-making processes; in such processes thevariants will typically be added during the mashing process.

Applications in detergent additives and detergent compositions forwashing or dishwashing: Owing to the improved washing and/or dishwashingperformance which will often be a consequence of improvements inproperties as discussed above, numerous α-amylase variants (includinghybrids) of the invention are particularly well suited for incorporationinto detergent compositions, e.g. detergent compositions intended forperformance in the pH range of 7-13, particularly the pH range of 8-11.According to the invention, the α-amylase variant may be added as acomponent of a detergent composition. As such, it may be included in thedetergent composition in the form of a detergent additive.

Thus, a further aspect of the invention relates to a detergent additivecomprising an α-amylase variant according to the invention. The enzymesmay be included in a detergent composition by adding separate additivescontaining one or more enzymes, or by adding a combined additivecomprising all of these enzymes. A detergent additive of the invention,i.e. a separated additive or a combined additive, can be formulated,e.g., as a granulate, liquid, slurry, etc. Preferred enzyme formulationsfor detergent additives are granulates (in particular non-dustinggranulates), liquids (in particular stabilized liquids), slurries orprotected enzymes (vide infra).

The detergent composition as well as the detergent additive mayadditionally comprise one or more other enzymes conventionally used indetergents, such as proteases, lipases, amylolytic enzymes, oxidases(including peroxidases), or cellulases.

It has been found that substantial improvements in washing and/ordishwashing performance may be obtained when α-amylase is combined withanother amylolytic enzyme, such as a pullulanase, an iso-amylase, abeta-amylase, an amyloglucosidase or a CGTase. Examples of commerciallyavailable amylolytic enzymes suitable for the given purpose are AMG™,Novamyl™ and Promozyme™, all of which available from Novo Nordisk A/S,Bagsvaerd, Denmark. Accordingly, a particular embodiment of theinvention relates to a detergent additive comprising an α-amylasevariant of the invention in combination with at least one otheramylolytic enzyme (e.g. chosen amongst those mentioned above).

Non-dusting granulates may be produced, e.g., as disclosed in U.S. Pat.No. 4,106,991 and U.S. Pat. No. 4,661,452, and may optionally be coatedby methods known in the art; further details concerning coatings aregiven below. When a combination of different detergent enzymes is to beemployed, the enzymes may be mixed before or after granulation.

Liquid enzyme preparations may, for instance, be stabilized by adding apolyol such as propylene glycol, a sugar or sugar alcohol, lactic acidor boric acid according to established methods. Other enzyme stabilizersare well known in the art. Protected enzymes may be prepared accordingto the method disclosed in EP 238 216.

As already indicated, a still further aspect of the invention relates toa detergent composition, e.g. for laundry washing, for dishwashing orfor hard-surface cleaning, comprising an α-amylase variant (includinghybrid) of the invention, and a surfactant.

The detergent composition of the invention may be in any convenientform, e.g. as powder, granules or liquid. A liquid detergent may beaqueous, typically containing up to 90% of water and 0-20% of organicsolvent, or non-aqueous, e.g. as described in EP Patent 120,659.

Detergent Compositions

When an α-amylase variant of the invention is employed as a component ofa detergent composition (e.g. a laundry washing detergent composition,or a dishwashing detergent composition), it may, for example, beincluded in the detergent composition in the form of a non-dustinggranulate, a stabilized liquid, or a protected enzyme. As mentionedabove, non-dusting granulates may be produced, e.g., as disclosed inU.S. Pat. Nos. 4,106,991 and 4,661,452 (both to Novo Industri A/S) andmay optionally be coated by methods known in the art. Examples of waxycoating materials are poly(ethylene oxide) products (polyethyleneglycol,PEG) with mean molecular weights of 1000 to 20000; ethoxylatednonylphenols having from 16 to 50 ethylene oxide units; ethoxylatedfatty alcohols in which the alcohol contains from 12 to 20 carbon atomsand in which there are 15 to 80 ethylene oxide units; fatty alcohols;fatty acids; and mono- and di- and triglycerides of fatty acids.Examples of film-forming coating materials suitable for application byfluid bed techniques are given in GB 1483591.

Enzymes added in the form of liquid enzyme preparations may, asindicated above, be stabilized by, e.g., the addition of a polyol suchas propylene glycol, a sugar or sugar alcohol, lactic acid or boric acidaccording to established methods. Other enzyme stabilizers are wellknown in the art.

Protected enzymes for inclusion in a detergent composition of theinvention may be prepared, as mentioned above, according to the methoddisclosed in EP 238,216.

The detergent composition of the invention may be in any convenientform. e.g. as powder, granules, paste or liquid. A liquid detergent maybe aqueous, typically containing up to 70% water and 0-30% organicsolvent, or nonaqueous.

The detergent composition comprises one or more surfactants, each ofwhich may be anionic, nonionic, cationic, or amphoteric (zwitterionic).The detergent will usually contain 0-50% of anionic surfactant such aslinear alkylbenzenesulfonate (LAS), alpha-olefinsulfonate (AOS), alkylsulfate (fatty alcohol sulfate) (AS), alcohol ethoxysulfate (AEOS orAES), secondary alkanesulfonales (SAS), alpha-sulfo fatty acid methylesters, alkyl- or alkenylsuccinic acid, or soap. It may also contain0-40% of nonionic surfactant such as alcohol ethoxylate (AEO or AE),alcohol propoxylate, carboxylated alcohol ethoxylates, nonylphenolethoxylate, alkyl polyglycoside, alkyldimethylamine oxide, ethoxylatedfatty acid monoethanolamide, fatty acid monoethanolamide, or polyhydroxyalkyl fatty acid amide (e.g. as described in WO 92/06154).

The detergent composition may additionally comprise one or more otherenzymes, such as pullulanase, esterase, lipase, cutinase, protease,cellulase, peroxidase, or oxidase, e.g., laccase.

Normally the detergent contains 1-65% of a detergent builder (althoughsome dishwashing detergents may contain even up to 90% of a detergentbuilder) or complexing agent such as zeolite, diphosphate, triphosphate,phosphonate, citrate, nitrilotriacetic acid (NTA),ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaaceticacid (DTMPA), alkyl- or alkenylsuccinic acid, soluble silicates orlayered silicates (e.g. SKS-6 from Hoechst).

The detergent builders may be subdivided into phosphorus-containing andnon-phosphorous-containing types. Examples of phosphorus-containinginorganic alkaline detergent builders include the water-soluble salts,especially alkali metal pyrophosphates, orthophosphates, polyphosphatesand phosphonates. Examples of non-phosphorus-containing inorganicbuilders include water-soluble alkali metal carbonates, borates andsilicates, as well as layered disilicates and the various types ofwater-insoluble crystalline or amorphous alumino silicates of whichzeolites are the best known representatives.

Examples of suitable organic builders include alkali metal, ammonium orsubstituted ammonium salts of succinates, malonates, fatty acidmalonates, fatty acid sulphonates, carboxymethoxy succinates,polyacetates, carboxylates, polycarboxylates, aminopolycarboxylates andpolyacetyl carboxylates.

The detergent may also be unbuilt, i.e. essentially free of detergentbuilder.

The detergent may comprise one or more polymers. Examples arecarboxymethylcellulose (CMC; typically in the form of the sodium salt),polyvinylpyrrolidone) (PVP), polyethyleneglycol (PEG), polyvinylalcohol) (PVA), polycarboxylates such as polyacrylates, polymaleates,maleic/acrylic acid copolymers and lauryl methacrylate/acrylic acidcopolymers.

The detergent composition may contain bleaching agents of thechlorine/bromine-type or the oxygen-type. The bleaching agents may becoated or encapsulated. Examples of inorganic chlorine/bromine-typebleaches are lithium, sodium or calcium hypochlorite or hypobromite aswell as chlorinated trisodium phosphate. The bleaching system may alsocomprise a H₂O₂ source such as perborate or percarbonate which may becombined with a peracid-forming bleach activator such astetraacetylethylenediamine (TAED) or nonanoyloxybenzenesulfonate (NOBS).

Examples of organic chlorine/bromine-type bleaches are heterocyclicN-bromo and N-chloro imides such as trichloroisocyanuric,tribromoisocyanuric, dibromoisocyanuric and dichloroisocyanuric acids,and salts thereof with water solubilizing cations such as potassium andsodium. Hydantoin compounds are also suitable. The bleaching system mayalso comprise peroxyacids of, e.g., the amide, imide, or sulfone type.

In dishwashing detergents the oxygen bleaches are preferred, for examplein the form of an inorganic persalt, preferably with a bleach precursoror as a peroxy acid compound. Typical examples of suitable peroxy bleachcompounds are alkali metal perborates, both tetrahydrates andmonohydrates, alkali metal percarbonates, persilicates andperphosphates. Preferred activator materials are TAED or NOBS.

The enzymes of the detergent composition of the invention may bestabilized using conventional stabilizing agents, e.g. a polyol such aspropylene glycol or glycerol, a sugar or sugar alcohol, lactic acid,boric acid, or a boric acid derivative such as, e.g., an aromatic borateester, and the composition may be formulated as described in, e.g., WO92/19709 and WO 92/19708. The enzymes of the invention may also bestabilized by adding reversible enzyme inhibitors, e.g., of the proteintype (as described in EP 0 544 777 B1) or the boronic acid type.

The detergent may also contain other conventional detergent ingredientssuch as, e.g., fabric conditioners including clays, deflocculantmaterial, foam boosters/foam depressors (in dishwashing detergents foamdepressors), suds suppressors, anti-corrosion agents, soil-suspendingagents, anti-soil-redeposition agents, dyes, dehydrating agents,bactericides, optical brighteners, or perfume.

The pH (measured in aqueous solution at use concentration) will usuallybe neutral or alkaline, e.g. in the range of 7-11.

Particular forms of laundry detergent compositions within the scope ofthe invention include:

1) A detergent composition formulated as a granulate having a bulkdensity of at least 600 g/l comprising

Linear alkylbenzenesulfonate (calculated as acid)  7-12% Alcoholethoxysulfate (e.g. C₁₂₋₁₈ alcohol, 1-2 EO) or 1-4% alkyl sulfate (e.g.C₁₆₋₁₈) Alcohol ethoxylate (e.g. C₁₄₋₁₅ alcohol, 7 EO) 5-9% Sodiumcarbonate (as Na₂CO₃) 14-20% Soluble silicate (as Na₂O,2SiO₂) 2-6%Zeolite (as NaAlSiO₄) 15-22% Sodium sulfate (as Na₂SO₄) 0-6% Sodiumcitrate/citric acid (as C₆H₅Na₃O₇/C₆H₈O₇)  0-15% Sodium perborate (asNaBO₃•H₂O) 11-18% TAED 2-6% Carboxymethylcellulose 0-2% Polymers (e.g.maleic/acrylic acid copolymer, PVP, 0-3% PEG) Enzymes (calculated aspure enzyme protein) 0.0001-0.1%   Minor ingredients (e.g. sudssuppressors, perfume, 0-5% optical brightener, photobleach)

2) A detergent composition formulated as a granulate having a bulkdensity of at least 600 g/l comprising

Linear alkylbenzenesulfonate (calculated as acid)  6-11% Alcoholethoxysulfate (e.g. C₁₂₋₁₈ alcohol, 1-2 EO or 1-3% alkyl sulfate (e.g.C₁₆₋₁₈) Alcohol ethoxylate (e.g. C₁₄₋₁₅ alcohol, 7 EO) 5-9% Sodiumcarbonate (as Na₂CO₃) 15-21% Soluble silicate (as Na₂O,2SiO₂) 1-4%Zeolite (as NaAlSiO₄) 24-34% Sodium sulfate (as Na₂SO₄)  4-10% Sodiumcitrate/citric acid (as C₆H₅Na₃O₇/C₆H₈O₇)  0-15% Carboxymethylcellulose0-2% Polymers (e.g. maleic/acrylic acid copolymer, PVP, 1-6% PEG)Enzymes (calculated as pure enzyme protein) 0.0001-0.1%   Minoringredients (e.g. suds suppressors, perfume) 0-5%

3) A detergent composition formulated as a granulate having a bulkdensity of at least 600 g/l comprising

Linear alkylbenzenesulfonate (calculated as acid) 5-9% Alcoholethoxylate (e.g. C₁₂₋₁₅ alcohol, 7 EO)  7-14% Soap as fatty acid (e.g.C₁₆₋₂₂ fatty acid) 1-3% Sodium carbonate (as Na₂CO₃) 10-17% Solublesilicate (as Na₂O,2SiO₂) 3-9% Zeolite (as NaAlSiO₄) 23-33% Sodiumsulfate (as Na₂SO4) 0-4% Sodium perborate (as NaBO₃•H₂O)  8-16% TAED2-8% Phosphonate (e.g. EDTMPA) 0-1% Carboxymethylcellulose 0-2% Polymers(e.g. maleic/acrylic acid copolymer, PVP, 0-3% PEG) Enzymes (calculatedas pure enzyme protein) 0.0001-0.1%   Minor ingredients (e.g. sudssuppressors, perfume, 0-5% optical brightener)

4) A detergent composition formulated as a granulate having a bulkdensity of at least 600 g/l comprising

Linear alkylbenzenesulfonate (calculated as acid)  8-12% Alcoholethoxylate (e.g. C₁₂₋₁₅ alcohol, 7 EO) 10-25% Sodium carbonate (asNa₂CO₃) 14-22% Soluble silicate (as Na₂O,2SiO₂) 1-5% Zeolite (asNaAlSiO₄) 25-35% Sodium sulfate (as Na₂SO₄)  0-10%Carboxymethylcellulose 0-2% Polymers (e.g. maleic/acrylic acidcopolymer, PVP, 1-3% PEG) Enzymes (calculated as pure enzyme protein)0.0001-0.1%   Minor ingredients (e.g. suds suppressors, perfume) 0-5%

5) An aqueous liquid detergent composition comprising

Linear alkylbenzenesulfonate (calculated as acid) 15-21% Alcoholethoxylate (e.g. C₁₂₋₁₅ alcohol, 7 EO or C₁₂₋₁₅ 12-18% alcohol, 5 EO)Soap as fatty acid (e.g. oleic acid)  3-13% Alkenylsuccinic acid(C₁₂₋₁₄)  0-13% Aminoethanol  8-18% Citric acid 2-8% Phosphonate 0-3%Polymers (e.g. PVP, PEG) 0-3% Borate (as B₄O₇ ²⁻) 0-2% Ethanol 0-3%Propylene glycol  8-14% Enzymes (calculated as pure enzyme protein)0.0001-0.1%   Minor ingredients (e.g. dispersants, suds 0-5%suppressors, perfume, optical brightener)

6) An aqueous structured liquid detergent composition comprising

Linear alkylbenzenesulfonate (calculated as acid) 15-21% Alcoholethoxylate (e.g. C₁₂₋₁₅ alcohol, 7 EO, or 3-9% C₁₂₋₁₅ alcohol, 5 EO)Soap as fatty acid (e.g. oleic acid)  3-10% Zeolite (as NaAlSiO₄) 14-22%Potassium citrate  9-18% Borate (as B₄O₇ ²⁻) 0-2% Carboxybethylcellulose0-2% Polymers (e.g. PEG, PVP) 0-3% Anchoring polymers such as, e.g.,lauryl 0-3% methacrylate/acrylic acid copolymer; molar ratio 25:1; MW3800 Glycerol 0-5% Enzymes (calculated as pure enzyme protein)0.0001-0.1%   Minor ingredients (e.g. dispersants, suds 0-5%suppressors, perfume, optical brighteners)

7) A detergent composition formulated as a granulate having a bulkdensity of at least 600 g/l comprising

Fatty alcohol sulfate  5-10% Ethoxylated fatty acid monoethanolamide3-9% Soap as fatty acid 0-3% Sodium carbonate (as Na₂CO₃)  5-10% Solublesilicate (as Na₂O,2SiO₂) 1-4% Zeolite (as NaAlSiO₄) 20-40% Sodiumsulfate (as Na₂SO₄) 2-8% Sodium perborate (as NaBO₃•H₂O) 12-18% TAED2-7% Polymers (e.g. maleic/acrylic acid copolymer, PEG) 1-5% Enzymes(calculated as pure enzyme protein) 0.0001-0.1%   Minor ingredients(e.g. optical brightener, suds 0-5% suppressors, perfume)

8) A detergent composition formulated as a granulate comprising

Linear alkylbenzenesulfonate (calculated as acid)  8-14% Ethoxylatedfatty acid monoethanolamide  5-11% Soap as fatty acid 0-3% Sodiumcarbonate (as Na₂CO₃)  4-10% Soluble silicate (as Na₂O,2SiO₂) 1-4%Zeolite (as NaAlSiO₄) 30-50% Sodium sulfate (as Na₂SO₄)  3-11% Sodiumcitrate (as C₆H₅Na₃O₇)  5-12% Polymers (e.g. PVP, maleic/acrylic acidcopolymer, 1-5% PEG) Enzymes (calculated as pure enzyme protein)0.0001-0.1%   Minor ingredients (e.g. suds suppressors, perfume) 0-5%

9) A detergent composition formulated as a granulate comprising

Linear alkylbenzenesulfonate (calculated as acid)  6-12% Nonionicsurfactant 1-4% Soap as fatty acid 2-6% Sodium carbonate (as Na₂CO₃)14-22% Zeolite (as NaAlSiO₄) 18-32% Sodium sulfate (as Na₂SO₄)  5-20%Sodium citrate (as C₆H₅Na₃O₇) 3-8% Sodium perborate (as NaBO₃•H₂O) 4-9%Bleach activator (e.g. NOBS or TAED) 1-5% Carboxymethylcellulose 0-2%Polymers (e.g. polycarboxylate or PEG) 1-5% Enzymes (calculated as pureenzyme protein) 0.0001-0.1%   Minor ingredients (e.g. opticalbrightener, perfume) 0-5%

10) An aqueous liquid detergent composition comprising

Linear alkylbenzenesulfonate (calculated as acid) 15-23% Alcoholethoxysulfate (e.g. C₁₂₋₁₅ alcohol, 2-3 EO)  8-15% Alcohol ethoxylate(e.g. C₁₂₋₁₅ alcohol, 7 EO, or 3-9% C₁₂₋₁₅ alcohol, 5 EO) Soap as fattyacid (e.g. lauric acid) 0-3% Aminoethanol 1-5% Sodium citrate  5-10%Hydrotrope (e.g. sodium toluene sulfonate) 2-6% Borate (as B₄O₇ ²⁻) 0-2%Carboxymethylcellulose 0-1% Ethanol 1-3% Propylene glycol 2-5% Enzymes(calculated as pure enzyme protein) 0.0001-0.1%   Minor ingredients(e.g. polymers, dispersants, 0-5% perfume, optical brighteners)

11) An aqueous liquid detergent composition comprising

Linear alkylbenzenesulfonate (calculated as acid) 20-32% Alcoholethoxylate (e.g. C₁₂₋₁₅ alcohol, 7 EO,  6-12% or C₁₂₋₁₅ alcohol, 5 EO)Aminoethanol 2-6% Citric acid  8-14% Borate (as B₄O₇ ²⁻) 1-3% Polymer(e.g. maleic/acrylic acid copolymer, 0-3% anchoring polymer such as,e.g., lauryl methacrylate/acrylic acid copolymer) Glycerol 3-8% Enzymes(calculated as pure enzyme protein) 0.0001-0.1%   Minor ingredients(e.g. hydrotropes, dispersants, 0-5% perfume, optical brighteners)

12) A detergent composition formulated as a granulate having a bulkdensity of at least 600 g/l comprising

Anionic surfactant (linear alkylbenzenesulfonate, 25-40% alkyl sulfate;alpha-olefinsulfonate, alpha-sulfo fatty acid methyl esters,alkanesulfonates, soap) Nonionic surfactant (e.g. alcohol ethoxylate) 1-10% Sodium carbonate (as Na₂CO₃)  8-25% Soluble silicates (as Na₂O,2SiO₂)  5-15% Sodium sulfate (as Na₂SO₄) 0-5% Zeolite (as NaAlSiO₄)15-28% Sodium perborate (as NaBO₃•4H₂O)  0-20% Bleach activator (TAED orNOBS) 0-5% Enzymes (calculated as pure enzyme protein) 0.0001-0.1%  Minor ingredients (e.g. perfume, optical brighteners) 0-3%

13) Detergent formulations as described in 1)-12) wherein all or part ofthe linear alkyl benzenesulfonate is replaced by (C₁₂-C₁₈) alkylsulfate.

14) A detergent composition formulated as a granulate having a bulkdensity of at least 600 g/l comprising

(C₁₂-C₁₈) alkyl sulfate  9-15% Alcohol ethoxylate 3-6% Polyhydroxy alkylfatty acid amide 1-5% Zeolite (as NaAlSiO₄) 10-20% Layered disilicate(e.g. SK56 from Hoechst) 10-20% Sodium carbonate (as Na₂CO₃)  3-12%Soluble silicate (as Na₂O,2SiO₂) 0-6% Sodium citrate 4-8% Sodiumpercarbonate 13-22% TAED 3-8% Polymers (e.g. polycarboxylates and PVP)0-5% Enzymes (calculated as pure enzyme protein) 0.0001-0.1%   Minoringredients (e.g. optical brightener, 0-5% photo bleach, perfume, sudssuppressors)

15) A detergent composition formulated as a granulate having a bulkdensity of at least 600 g/l comprising

(C₁₂-C₁₈) alkyl sulfate 4-8% Alcohol ethoxylate 11-15% Soap 1-4% ZeoliteMAP or zeolite A 35-45% Sodium carbonate (as Na₂CO₃) 2-8% Solublesilicate (as Na₂O,2SiO₂) 0-4% Sodium percarbonate 13-22% TAED 1-8%Carboxymethyl cellulose 0-3% Polymers (e.g. polycarboxylates and PVP)0-3% Enzymes (calculated as pure enzyme protein) 0.0001-0.1%   Minoringredients (e.g. optical brightener, 0-3% phosphonate, perfume)

16) Detergent formulations as described in 1)-15) which contain astabilized or encapsulated peracid, either as an additional component oras a substitute for already specified bleach systems.

17) Detergent compositions as described in 1), 3), 7), 9) and 12)wherein perborate is replaced by percarbonate.

18) Detergent compositions as described in 1), 3), 7), 9), 12), 14) and15) which additionally contain a manganese catalyst. The manganesecatalyst may, e.g., be one of the compounds described in “Efficientmanganese catalysts for low-temperature bleaching”, Nature 369, 1994,pp. 637-639.

19) Detergent composition formulated as a nonaqueous detergent liquidcomprising a liquid nonionic surfactant such as, e.g., linearalkoxylated primary alcohol, a builder system (e.g. phosphate), enzymeand alkali. The detergent may also comprise anionic surfactant and/or ableach system.

Particular forms of dishwashing detergent compositions within the scopeof the invention include:

1) Powder Automatic Dishwashing Composition

Nonionic surfactant 0.4-2.5% Sodium metasilicate  0-20% Sodiumdisilicate  3-20% Sodium triphosphate 20-40% Sodium carbonate  0-20%Sodium perborate 2-9% Tetraacetylethylenediamine (TAED) 1-4% Sodiumsulphate  5-33% Enzymes 0.0001-0.1%  

2) Powder Automatic Dishwashing Composition

Nonionic surfactant (e.g. alcohol ethoxylate) 1-2% Sodium disilicate 2-30% Sodium carbonate 10-50% Sodium phosphonate 0-5% Trisodium citratedihydrate  9-30% Nitrilotrisodium acetate (NTA)  0-20% Sodium perboratemonohydrate  5-10% Tetraacetylethylenediamine (TAED) 1-2% Polyacrylatepolymer (e.g. maleic acid/  6-25% acrylic acid copolymer) Enzymes0.0001-0.1%   Perfume 0.1-0.5% Water 5-10 

3) Powder Automatic Dishwashing Composition

Nonionic surfactant 0.5-2.0% Sodium disilicate 25-40% Sodium citrate30-55% Sodium carbonate  0-29% Sodium bicarbonate  0-20% Sodiumperborate monohydrate  0-15% Tetraacetylethylenediamine (TAED) 0-6%Maleic acid/acrylic acid copolymer 0-5% Clay 1-3% Poly(amino acids) 0-20% Sodium polyacrylate 0-8% Enzymes 0.0001-0.1%  

4) Powder Automatic Dishwashing Composition

Nonionic surfactant 1-2% Zeolite MAP 15-42% Sodium disilicate 30-34%Sodium citrate  0-12% Sodium carbonate  0-20% Sodium perboratemonohydrate  7-15% Tetraacetylethylenediamine (TAED) 0-3% Polymer 0-4%Maleic acid/acrylic acid copolymer 0-5% Organic phosphonate 0-4% Clay1-2% Enzymes 0.0001-0.1%   Sodium sulphate Balance

5) Powder Automatic Dishwashing Composition

Nonionic surfactant 1-7% Sodium disilicate 18-30% Trisodium citrate10-24% Sodium carbonate 12-20% Monopersulphate (2KHSO₅•KHSO₄•K₂SO₄)15-21% Bleach stabilizer 0.1-2%   Maleic acid/acrylic acid copolymer0-6% Diethylenetriaminepentaacetate, pentasodium salt   0-2.5% Enzymes0.0001-0.1%   Sodium sulphate, water Balance6) Powder and Liquid Dishwashing Composition with Cleaning SurfactantSystem

Nonionic surfactant   0-1.5% Octadecyl dimethylamine N-oxide dihydrate0-5% 80:20 wt. C18/C16 blend of octadecyl dimethylamine 0-4% N-oxidedihydrate and hexadecyldimethyl amine N- oxide dihydrate 70:30 wt.C18/C16 blend of octadecyl bis 0-5% (hydroxyethyl)amine N-oxideanhydrous and hexadecyl bis (hydroxyethyl)amine N-oxide anhydrousC₁₃-C₁₅ alkyl ethoxysulfate with an average degree  0-10% ofethoxylation of 3 C₁₂-C₁₅ alkyl ethoxysulfate with an average degree0-5% of ethoxylation of 3 C₁₃-C₁₅ ethoxylated alcohol with an averagedegree 0-5% of ethoxylation of 12 A blend of C₁₂-C₁₅ ethoxylatedalcohols with an   0-6.5% average degree of ethoxylation of 9 A blend ofC₁₃-C₁₅ ethoxylated alcohols with an 0-4% average degree of ethoxylationof 30 Sodium disilicate  0-33% Sodium tripolyphosphate  0-46% Sodiumcitrate  0-28% Citric acid  0-29% Sodium carbonate  0-20% Sodiumperborate monohydrate   0-11.5% Tetraacetylethylenediamine (TAED) 0-4%Maleic acid/acrylic acid copolymer   0-7.5% Sodium sulphate   0-12.5%Enzymes 0.0001-0.1%  

7) Non-Aqueous Liquid Automatic Dishwashing Composition

Liquid nonionic surfactant (e.g. alcohol ethoxylates)  2.0-10.0% Alkalimetal silicate  3.0-15.0% Alkali metal phosphate 20.0-40.0% Liquidcarrier selected from higher glycols, 25.0-45.0% polyglycols,polyoxides, glycolethers Stabilizer (e.g. a partial ester of phosphoricacid and 0.5-7.0% a C₁₆-C₁₈ alkanol) Foam suppressor (e.g. silicone)  0-1.5% Enzymes 0.0001-0.1%  

8) Non-Aqueous Liquid Dishwashing Composition

Liquid nonionic surfactant (e.g. alcohol ethoxylates)  2.0-10.0% Sodiumsilicate  3.0-15.0% Alkali metal carbonate  7.0-20.0% Sodium citrate0.0-1.5% Stabilizing system (e.g. mixtures of finely divided 0.5-7.0%silicone and low molecular weight dialkyl polyglycol ethers) Lowmolecule weight polyacrylate polymer  5.0-15.0% Clay gel thickener (e.g.bentonite)  0.0-10.0% Hydroxypropyl cellulose polymer 0.0-0.6% Enzymes0.0001-0.1%   Liquid carrier selected from higher lycols, Balancepolyglycols, polyoxides and glycol ethers

9) Thixotropic Liquid Automatic Dishwashing Composition

C₁₂-C₁₄ fatty acid   0-0.5% Block co-polymer surfactant  1.5-15.0%Sodium citrate  0-12% Sodium tripolyphosphate  0-15% Sodium carbonate0-8% Aluminum tristearate   0-0.1% Sodium cumene sulphonate   0-1.7%Polyacrylate thickener 1.32-2.5%  Sodium polyacrylate 2.4-6.0% Boricacid   0-4.0% Sodium formate   0-0.45% Calcium formate   0-0.2% Sodiumn-decydiphenyl oxide disulphonate   0-4.0% Monoethanol amine (MEA)  0-1.86% Sodium hydroxide (50%) 1.9-9.3% 1,2-Propanediol   0-9.4%Enzymes 0.0001-0.1%   Suds suppressor, dye, perfumes, water Balance

10) Liquid Automatic Dishwashing Composition

Alcohol ethoxylate  0-20% Fatty acid ester sulphonate  0-30% Sodiumdodecyl sulphate  0-20% Alkyl polyglycoside  0-21% Oleic acid  0-10%Sodium disilicate monohydrate 18-33% Sodium citrate dihydrate 18-33%Sodium stearate   0-2.5% Sodium perborate monohydrate  0-13%Tetraacetylethylenediamine (TAED) 0-8% Maleic acid/acrylic acidcopolymer 4-8% Enzymes 0.0001-0.1%  

11) Liquid Automatic Dishwashing Composition Containing Protected BleachParticles

Sodium silicate  5-10% Tetrapotassium pyrophosphate 15-25% Sodiumtriphosphate 0-2% Potassium carbonate 4-8% Protected bleach particles,e.g. chlorine  5-10% Polymeric thickener 0.7-1.5% Potassium hydroxide0-2% Enzymes 0.0001-0.1%   Water Balance

11) Automatic dishwashing compositions as described in 1), 2), 3), 4),6) and 10), wherein perborate is replaced by percarbonate.

12) Automatic dishwashing compositions as described in 1)-6) whichadditionally contain a manganese catalyst. The manganese catalyst may,e.g., be one of the compounds described in “Efficient manganesecatalysts for low-temperature bleaching”, Nature 369, 1994, pp. 637-639.

An α-amylase variant of the invention may be incorporated inconcentrations conventionally employed in detergents. It is at presentcontemplated that, in the detergent composition of the invention, theα-amylase variant may be added in an amount corresponding to 0.00001-1mg (calculated as pure enzyme protein) of α-amylase per liter ofwash/dishwash liquor.

The present invention is further described with reference to theappended drawing, in which:

FIG. 1 is an alignment of the amino acid sequences of four parentα-amylases in the context of the invention. The numbers on the extremeleft designate the respective amino acid sequences as follows:

1: the amino acid sequence shown in SEQ ID No. 1;

2: the amino acid sequence shown in SEQ ID No. 2;

3: the amino acid sequence shown in SEQ ID No. 3; and

4: the amino acid sequence shown in SEQ ID No. 7.

The numbers on the extreme right of the figure give the running totalnumber of amino acids for each of the sequences in question. It shouldbe noted that for the sequence numbered 3 (corresponding to the aminoacid sequence shown in SEQ ID No. 3), the alignment results in “gaps” atthe positions corresponding to amino acid No. 1 and amino acid No. 175,respectively, in the sequences numbered 1 (SEQ ID No. 1), 2 (SEQ ID No.2) and 4 (SEQ ID No. 7).

FIG. 2 is a restriction map of plasmid pTVB106.

FIG. 3 is a restriction map of plasmid pPM103.

FIG. 4 is a restriction map of plasmid pTVB112.

FIG. 5 is a restriction map of plasmid pTVB114.

EXPERIMENTAL SECTION

The preparation, purification and sequencing of the parent α-amylaseshaving the amino acid sequences shown in SEQ ID No. 1 and SEQ ID No. 2(from Bacillus strains NClB 12512 and NCIB 12513, respectively) isdescribed in WO 95/26397. The pI values and molecular weights of thesetwo parent α-amylases (given in WO 95/26397) are as follows:

SEQ ID No. 1: pI about 8.8-9.0 (determined by isoelectric focusing onLKB Ampholine™ PAG plates): molecular weight approximately 55 kD(determined by SDS-PAGE).

SEQ ID No. 2: pI about 5.8 (determined by isoelectric focusing on LKBAmpholine™ PAG plates); molecular weight approximately 55 kD (determinedby SDS-PAGE).

Purification of α-Amylase Variants of the Invention

The construction and expression of variants according to the inventionis described in Example 2, below. The purification of variants of theinvention is illustrated here with reference to variants of the aminoacid sequences shown in SEQ ID No. 1 and SEQ ID No. 2, respectively:

Purification of SEQ ID No. 1 variants (pI approx. 9.0): The fermentationliquid containing the expressed α-amylase variant is filtered, andammonium sulfate is added to a concentration of 15% of saturation. Theliquid is then applied onto a hydrophobic column (Toyopearlbutyl/TOSOH). The column is washed with 20 mM dimethyl-glutaric acidbuffer, pH 7.0. The α-amylase is bound very tightly, and is eluted with25% w/w 2-propanol in 20 mM dimethylglutaric acid buffer, pH 7.0. Afterelution, the 2-propanol is removed by evaporation and the concentrate isapplied onto a cation exchanger (S-Sepharose™ FF, Pharmacia, Sweden)equilibrated with 20 mM dimethylglutaric acid buffer, pH 6.0.

The amylase is eluted using a linear gradient of 0-250 mM NaCl in thesame buffer. After dialysis against 10 mM borate/KCl buffer, pH 8.0, thesample is adjusted to pH 9.6 and applied to an anion exchanger(Q-Sepharose™ FF, Pharmacia) equilibrated with 10 mM borate/KCl buffer,pH 9.6. The amylase is eluted using a linear gradient of 0-250 mM NaCl.The pH is adjusted to 7.5. The α-amylase is pure as judged by rSDS-PAGE.All buffers contain 2 mM CaCl₂ in order to stabilize the amylase.

Purification of SEQ ID No. 2 variants (pI approx. 5,8): The fermentationliquid containing the expressed α-amylase variant is filtered, andammonium sulfate is added to a concentration of 15% of saturation. Theliquid is then applied onto a hydrophobic column (Toyopearlbutyl/TOSOH). The bound amylase is eluted with a linear gradient of15%-0% w/w ammonium sulfate in 10 mM Tris buffer, pH 8.0. After dialysisof the eluate against 10 mM borate/KCl buffer, pH 8.0, the liquid isadjusted to pH 9.6 and applied onto an anion exchanger (Q-Sepharose™ FF,Pharmacia) equilibrated with the same buffer. The amylase is step-elutedusing 150 mM NaCl.

After elution the amylase sample is dialyzed against the same buffer, pH8.0, in order to remove the NaCl. After dialysis, the pH is adjusted to9.6 and the amylase is bound once more onto the anion exchanger. Theamylase is eluted using a linear gradient of 0-250 mM NaCl. The pH isadjusted to 7.5. The amylase is pure as judged by rSDS-PAGE. All bufferscontain 2 mM CaCl₂ in order to stabilize the amylase.

Determination of α-Amylase Activity

α-Amylase activity is determined by a method employing Phadebas® tabletsas substrate. Phadebas tablets (Phadebas® Amylase Test, supplied byPharmacia Diagnostic) contain a cross-linked insoluble blue-coloredstarch polymer which has been mixed with bovine serum albumin and abuffer substance and tableted.

For the determination of every single measurement one tablet issuspended in a tube containing 5 ml 50 mM Britton-Robinson buffer (50 mMacetic acid, 50 mM phosphoric acid, 50 mM boric acid, 0.1 mM CaCl₂, pHadjusted to the value of interest with NaOH). The test is performed in awater bath at the temperature of interest. The α-amylase to be tested isdiluted in x ml of 50 mM Britton-Robinson buffer. 1 ml of this α-amylasesolution is added to the 5 ml 50 mM Britton-Robinson buffer. The starchis hydrolyzed by the α-amylase giving soluble blue fragments. Theabsorbance of the resulting blue solution, measuredspectrophotometrically at 620 nm, is a function of the α-amylaseactivity.

It is important that the measured 620 nm absorbance after 15 minutes ofincubation (testing time) is in the range of 0.2 to 2.0 absorbance unitsat 620 nm. In this absorbance range there is linearity between activityand absorbance (Lambert-Beer law). The dilution of the enzyme musttherefore be adjusted to fit this criterion.

Under a specified set of conditions (temp., pH, reaction time, bufferconditions) 1 mg of a given α-amylase will hydrolyze a certain amount ofsubstrate and a blue color will be produced. The color intensity ismeasured at 620 nm. The measured absorbance is directly proportional tothe specific activity (activity/mg of pure α-amylase protein) of theα-amylase in question under the given set of conditions. Thus testingdifferent α-amylases of interest (including a reference α-amylase, inthis case the parent α-amylase in question) under identical conditions,the specific activity of each of the α-amylases at a given temperatureand at a given pH can be compared directly, and the ratio of thespecific activity of each of the α-amylases of interest relative to thespecific activity of the reference α-amylase can be determined.

Mini Dishwashing Assay

The following mini dishwashing assay was used: A suspension of starchymaterial was boiled and cooled to 20° C. The cooled starch suspensionwas applied on small, individually identified glass plates (approx. 2×2cm) and dried at a temperature of ca. 140° C. in a drying cabinet. Theindividual plates were then weighed. For assay purposes, a solution ofstandard European-type automatic dishwashing detergent (5 g/l) having atemperature of 55° C. was prepared. The detergent was allowed adissolution time of 1 minute, after which the α-amylase in question wasadded to the detergent solution (contained in a beaker equipped withmagnetic stirring) so as to give an enzyme concentration of 0.5 mg/l. Atthe same time, the weighed glass plates, held in small supportingclamps, were immersed in a substantially vertical position in theα-amylase/detergent solution, which was then stirred for 15 minutes at55° C. The glass plates were then removed from the α-amylase/detergentsolution, rinsed with distilled water, dried at 60° C. in a dryingcabinet and re-weighed. The performance of the α-amylase in question[expressed as an index relative to a chosen reference α-amylase (index100)—in the example below (Example 1) the parent α-amylase having theamino acid sequence shown in SEQ ID No. 1] was then determined from thedifference in weight of the glass plates before and after treatment, asfollows:

${Index} = {\frac{{weight}\mspace{14mu} {loss}\mspace{14mu} {for}\mspace{14mu} {plate}\mspace{14mu} {treated}\mspace{14mu} {with}\mspace{14mu} \alpha \text{-}{amylase}}{{weight}\mspace{14mu} {loss}\mspace{14mu} {for}\mspace{14mu} {plate}\mspace{14mu} {treated}\mspace{14mu} {with}\mspace{14mu} {reference}} \cdot 100}$

The following examples further illustrate the present invention. Theyare not intended to be in any way limiting to the scope of the inventionas claimed.

Example 1 Mini Dishwashing Test of Variants of Parent α-Amylase Havingthe Amino Acid Sequence Shown in SEQ ID No. 1

The above-described mini dishwashing test was performed at pH 10.5 withthe parent α-amylase having the amino acid sequence shown in SEQ ID No.1 and the following variants thereof (the construction and purificationof which is described below): T183*+G184*; Y243F; and K269R. The testgave the following results:

Parent (SEQ ID No. 1) Index: 100 T183* + G184* Index: 120 Y243F Index:120 K269R Index: 131

It is apparent that the each of the tested variants T183*+G184* (whichexhibits, inter alia, higher thermal stability than the parentα-amylase), Y243F (which exhibits lower calcium ion dependency than theparent α-amylase) and K269R (which exhibits lower calcium ion dependencyand higher stability at high pH than the parent α-amylase) exhibitssignificantly improved dishwashing performance relative to the parentα-amylase.

Example 2 Construction of Variants of the Parent α-Amylases Having theAmino Acid Sequences Shown in SEQ ID No. 1 and SEQ ID No. 2,Respectively

Primers: DNA primers employed in the construction of variants asdescribed below include the following [all DNA primers are written inthe direction from 5′ to 3′ (left to right); P denotes a 5′ phosphate]:

#7113: GCT GCG GTG ACC TCT TTA AAA AAT AAC GGC Y296: CC ACC GCT ATT AGATGC ATT GTA C #6779: CTT ACG TAT GCA GAC GTC GAT ATG GAT CAC CC #6778: GATC CAT ATC GAC GTC TGC ATA CGT AAG ATA GTC #3811: TT A(C/G)G GGC AAGGCC TGG GAC TGG #7449: C CCA GGC CTT GCC C(C/G)T AAA TTT ATA TAT TTT GTTTTG #3810: G GTT TCG GTT CGA AGG ATT CAC TTC TAC CGC #7450: GCG GTA GAAGTG AAT CCT TCG AAC CGA AAC CAG B1: GGT ACT ATC GTA ACA ATG GCC GAT TGCTGA CGC TGT TAT TTG C #6616: P CTG TGA CTG GTG AGT ACT CAA CCA AGT C#8573: CTA CTT CCC AAT CCC AAG CTT TAC CTC GGA ATT TG #8569: CAA ATT CCGAGG TAA AGC TTG GGA TTG GGA AGT AG #8570: TTG AAC AAC CGT TCC ATT AAGAAG

A: Construction of Variants of the Parent α-Amylase Having the AminoAcid Sequence Shown in SEQ ID No. 1

Description of plasmid pTVB106: The parent α-amylase having the aminoacid sequence shown in SEQ ID No. 1 and variants thereof are expressedfrom a plasmid-borne gene, SF16, shown in FIG. 2. The plasmid, pTVB106,contains an origin of replication obtained from plasmid pUB110 (Gryczanet al., 1978) and the cat gene conferring resistance towardschloramphenicol. Secretion of the amylase is aided by the Termamyl™signal sequence that is fused precisely, i.e. codon No. 1 of the matureprotein, to the gene encoding the parent α-amylase having the nucleotideand amino acid sequence (mature protein) shown in SEQ ID No. 4 and SEQID No. 1, respectively. The Termamyl promoter initiates transcription ofthe gene.

Plasmid pTVB106 is similar to pDN1528 (see laid-open Danish patentapplication No. 1155/94). Some unique restriction sites are indicated onthe plasmid map in FIG. 2, including BstBI, BamHI, BstEII, EcoNI, DrdI,AflIII, DraIII, XmaI, SalI and BglII.

Construction of variant M202T: The PCR overlap extension mutagenesismethod is used to construct this variant (Higuchi et al., 1988). Anapproximately 350 by DNA fragment of pTVB106 is amplified in a PCRreaction A using primers #7113 and mutagenic primer #6778. In a similarPCR reaction B, an approximately 300 by DNA fragment is amplified usingprimers Y296 and #6779. The complete DNA fragment spanning the mutationsite (M202) from primer #7113 to primer Y296 is amplified in PCR C usingthese primers and purified DNA fragments from reactions A and B.

PCR C DNA is digested with restriction endonucleases BstEII and AflIII,and the 480 by fragment is ligated with plasmid pTVB106 digested withthe same enzymes and transformed into a low-protease and low-amylaseBacillus subtilis strain (e.g. strain SHA273 mentioned in WO 92/11357).

Other M202 variants are constructed in a similar manner.

Construction of variants T183*+G184* and R181*+G182*: The PCR overlapextension mutagenesis method is used to construct these variants(Higuchi et al., 1988). The mutagenic oligonucleotides are synthesizedusing a mixture (equal parts) of C and G in one position; two differentmutations can therefore be constructed by this procedure. Anapproximately 300 by DNA fragment of pTVB106 is amplified in a PCRreaction A using primers #7113 and mutagenic primer #7449. In a similarPCR reaction B, an approximately 400 by DNA fragment is amplified usingprimers Y296 and #3811. The complete DNA fragment spanning the mutationsite (amino acids 181-184) from primer #7113 to primer Y296 is amplifiedin PCR C using these primers and purified DNA fragments from reactions Aand B.

PCR C DNA is digested with restriction endonucleases BstEII and AflIIIand the 480 by fragment is ligated with plasmid pTVB106 digested withthe same enzymes and transformed into a low-protease and low-amylase B.subtilis strain (e.g. strain SHA273 mentioned in WO 92/11357).Sequencing of plasmid DNA from these transformants identifies the twocorrect mutations: i.e. R181*+G182* and T183*+G184*.

Construction of variant R124P: The PCR overlap extension mutagenesismethod is used to construct this variant in a manner similar to theconstruction of variant M202T (vide supra). PCR reaction A (with primers#3810 and B1) generates an approximately 500 by fragment, and PCRreaction B (primers 7450 and Y296) generates an approximately 550 byfragment. PCR reaction C based on the product of PCR reaction A and Band primers B1 and Y296 is digested with restriction endonucleasesBstEII and AflIII, and the resulting 480 by fragment spanning amino acidposition 124 is subcloned into pTVB106 digested with the same enzymesand transformed into B. subtilis as previously described.

Construction of variant R124P+T183*+G184*: For the construction of thevariant combining the R124P and the T183*+G184* mutations, two EcoNIrestriction sites (one located at position 1.774 kb, i.e. between theR124P mutation and the T183*+G184* mutation, and one located at position0.146 kb) were utilized. The approximately 1630 by EcoNI fragment of thepTVB106-like plasmid containing the T183*+G184* mutation was subclonedinto the vector part (approximately 3810 by DNA fragment containing theorigin of replication) of another pTVB106-like plasmid containing theR124P mutation digested with the same enzyme. Transformation intoBacillus subtilis was carried out as previously described.

Construction of variants G182*+G184*; R181 *+1183*: Y243F: K269R: andL351C+M430C: These variants were constructed as follows:

A specific mutagenesis vector containing a major part of the codingregion for the amino acid sequence shown in SEQ ID No. 1 was prepared.The important features of this vector (which is denoted pPM103) includean origin of replication derived from the pUC plasmid, the cat geneconferring resistance towards chloramphenicol and aframeshift-mutation-containing version of the bla gene, the wild-typeversion of which normally confers resistance towards ampicillin (amp^(R)phenotype). This mutated version of the bla gene results in an amp^(S)phenotype. The plasmid pPM103 is shown in FIG. 3, and the E. coli originof replication, the 5′-truncated version of the SF16 amylase gene, andori, bla, cat and selected restriction sites are indicated on theplasmid.

Mutations are introduced in the gene of interest as described by Dengand Nickoloff [Anal. Biochem. 200 (1992), pp. 81-88], except thatplasmids with the “selection primer” (#6616) incorporated are selectedbased on the amp^(R) phenotype of transformed E. coli cells harboring aplasmid with a repaired bla gene instead of using the selection byrestriction-enzyme digestion outlined by Deng and Nickoloff. Chemicalsand enzymes used for the mutagenesis were obtained from the Chameleon™mutagenesis kit from Stratagene (catalogue number 200509).

After verification of the DNA sequence in variant plasmids, thetruncated gene containing the desired alteration is subcloned from thepPM103-like plasmid into pTVB106 as an approximately 1440 by BstBI-SalIfragment and transformed into Bacillus subtilis for expression of thevariant enzyme.

For the construction of the pairwise deletion variant G182*+G184*, thefollowing mutagenesis primer was used:

P CTC TGT ATC GAC TTC CCA GTC CCA AGC TTT TGT CCT GAA TTT ATA TAT TTTGTT TTG AAG

For the construction of the pairwise deletion variant R181*+T183*, thefollowing mutagenesis primer was used:

P CTC TGT ATC GAC TTC CCA GTC CCA AGC TTT GCC TCC GAA TTT ATA TAT TTTGTT TTG AAG

For the construction of the substitution variant Y243F, the followingmutagenesis primer was used:

P ATG TGT AAG CCA ATC GCG AGT AAA GCT AAA TTT TAT ATG TTT CAC TGC ATC

For the construction of the substitution variant K269R, the followingmutagenesis primer was used:

P GC ACC AAG GTC ATT TCG CCA GAA TTC AGC CAC TG

For the construction of the pairwise substitution variant L351C+M430C,the following mutagenesis primers were used simultaneously:

1) P TGT CAG AAC CAA CGC GTA TGC ACA TGG TTT AAA CCA TTG 2) P ACC ACCTGG ACC ATC GCT GCA GAT GGT GGC AAG GCC TGA ATT

Construction of variant L351C+M430C+T183*+G184*: This variant wasconstructed by combining the L351C+M430C pairwise substitution mutationand the T183*+G184* pairwise deletion mutation by subcloning anapproximately 1430 by HindIII-AflIII fragment containing L351C+M430Cinto a pTVB106-like plasmid (with the T183*+G184* mutations) digestedwith the same enzymes.

Construction of variant Y243F+T183*+G184*: This variant was constructedby combining the Y243F mutation and the T183*+G184* mutation bysubcloning an approximately 1148 by DrdI fragment containing T183*+G184*into a pTVB106-like plasmid (with the Y243 mutation) digested with thesame enzyme.

Bacillus subtilis transformants were screened for α-amylase activity onstarch-containing agar plates and the presence of the correct mutationswas checked by DNA sequencing.

Construction of variant Y243F+T183*+G184*+L351C+M430C: The L351C+M430Cpairwise substitution mutation was subcloned as an approximately 470 byXmaI-SalI fragment into a pTVB106-like vector (containingY243F+T183*+G184*) digested with the same enzymes.

Construction of variant Y243F+T183*+G184*+L351C+M430C+Q391E+K444Q: ApPM103-like vector containing the mutationsY243F+T183*+G184*+L351C+M430C was constructed by substituting thetruncated version of SF16 in pPM103 with the approximately 1440 byBstBI-SalI fragment of the pTVB106-like vector containing the fivemutations in question. The Q391E and K444Q mutations were introducedsimultaneously into the pPM103-like vector (containingY243F+T183*+G184*+L351C+M430C) by the use of the following twomutagenesis primers in a manner similar to the previously describedmutagenesis on pPM103:

P GGC AAA AGT TTG ACG TGC CTC GAG AAG AGG GTC TAT P TTG TCC CGC TTT ATTCTG GCC AAC ATA CAT CCA TTT

B: Construction of Variants of the Parent α-Amylase Having the AminoAcid Sequence Shown in SEQ ID No. 2

Description of plasmid pTVB112: A vector, denoted pTVB112, to be usedfor the expression in B. subtilis of the α-amylase having the amino acidsequence shown in SEQ ID No. 2 was constructed. This vector is verysimilar to pTVB106 except that the gene encoding the mature α-amylase ofSEQ ID No. 2 is inserted between the PstI and the HindIII sites inpTVB106. Thus, the expression of this α-amylase (SEQ ID No. 2) is alsodirected by the amyL promoter and signal sequence. The plasmid pTVB112is shown in FIG. 4.

Construction of variant D183*+G184*: The construction of this variantwas achieved using the PCR overlap extension mutagenesis method referredto earlier (vide supra). Primers #8573 and B1 were used in PCR reactionA, and primers #8569 and #8570 were used in PCR reaction B. The purifiedfragments from reaction A and reaction B and primers 1B and #8570 wereused in PCR reaction C, resulting in an approximately 1020 by DNAfragment. This fragment was digested with restriction endonucleases PstIand MluI, and subcloned into the expression vector and transformed intoB. subtilis.

Construction of further variants: By analogy with the construction (videsupra) of the plasmid pPM103 used in the production of mutants of theamino acid sequence of SEQ ID No. 1, a plasmid (denoted pTVB114; shownin FIG. 5) was constructed for the continued mutagenesis on variantD183*+G184* (SEQ.ID No. 2). Mutations were introduced in pTVB114 (SEQ IDNo. 2; D183*+G184*) in a manner similar to that for pPM103 (SEQ ID No.1).

For the construction of the pairwise deletion variants R181*+D183* andR181*+G182*, it was chosen to alter the flanking amino acids in thevariant D183*+G184* instead of deleting the specified amino acids in thewild type gene for SEQ ID No. 2. The following mutagenesis primer wasused for the mutagenesis with pTVB114 as template:

PCC CAA TCC CAA GCT TTA CCA (T/C)CG AAC TTG TAG ATA CG

The presence of a mixture of two bases (T/C) at one position allows forthe presence of two different deletion flanking amino acid based on onemutagenesis primer. DNA sequencing of the resulting plasmids verifiesthe presence of either the one or the other mutation. The mutated geneof interest is subcloned as a PstI-DraIII fragment into pTVB112 digestedwith the same enzymes and transformed into B. subtilis.

For the construction of G182*+G184* and R181*+G184*, the followingmutagenesis primer was used with pTVB114 as template:

PCC CAA TCC CAA GCT TTA TCT C(C/G)G AAC TTG TAG ATA CG

As before, the presence of a mixture of two bases (C/G) at one positionallows for the presence of two different deletion flanking amino acidbased on one mutagenesis primer. DNA sequencing of the resultingplasmids verifies the presence of either the one or the other mutation.The mutated gene of interest is subcloned as a PstI-DraIII fragment intopTVB112 digested with the same enzymes and transformed into B. subtilis.

For the construction of D183*+G184*+M202L the following mutagenesisprimer was used:

PGA TCC ATA TCG ACG TCT GCA TAC AGT AAA TAA TC

For the construction of D183*+G184*+M2021 the following mutagenesisprimer was used:

PGA TCC ATA TCG ACG TCT GCA TAA ATT AAA TAA TC

Example 3 Determination of Oxidation Stability of M202 SubstitutionVariants of the Parent α-Amylases having the Amino Acid Sequences Shownin SEQ ID No. 1 and SEQ ID No. 2 A: Oxidation Stability of Variants ofthe Sequence in SEQ ID No. 1

The measurements were made using solutions of the respective variants in50 mM Britton-Robinson buffer (50 mM acetic acid, 50 mM phosphoric acid,50 mM boric acid, 0.1 mM CaCl₂, pH adjusted to the value of interestwith NaOH), pH 9.0, to which hydrogen peroxide was added (at time t=0)to give a final concentration of 200 mM H₂O₂. The solutions were thenincubated at 40° C. in a water bath.

After incubation for 5, 10, 15 and 20 minutes after addition of hydrogenperoxide, the residual α-amylase activity was measured using thePhadebas assay described above. The residual activity in the samples wasmeasured using 50 mM Britton-Robinson buffer, pH 7.3, at 37° C. (seeNovo analytical publication AF207-1/1, available on request from NovoNordisk A/S). The decline in activity was measured relative to acorresponding reference solution of the same enzyme at 0 minutes whichwas not incubated with hydrogen peroxide (100% activity).

The percentage of initial activity as a function of time is shown in thetable below for the parent enzyme (SEQ ID No. 1) and for the variants inquestion.

% Activity after incubation for (minutes) Variant 0 5 10 15 20 M202L 10090 72 58 27 M202F 100 100 87 71 43 M202A 100 99 82 64 30 M202I 100 91 7559 28 M2O2T 100 87 65 49 20 M202V 100 100 87 74 43 M202S 100 100 85 6834 Parent 100 51 26 13 2

All the M202 substitution variants tested clearly exhibit significantlyimproved stability towards oxidation relative to the parent α-amylase(SEQ ID No. 1).

B: Oxidation Stability of Variants of the Sequence in SEQ ID No. 2

Measurements were made as described above using the parent α-amylase inquestion (SEQ ID No. 2), the variant M202L+D183*+G184* (designated L inthe table below) and the variant M2021+D183*+G184* (designated I in thetable below), respectively. In this case, incubation times (afteraddition of hydrogen peroxide) of 5, 10, 15 and 30 minutes wereemployed. As in the table above, the percentage of initial activity as afunction of time is shown in the table below for the parent enzyme andfor the variants in question.

% Activity after incubation for (minutes) Variant 0 5 10 15 30 L 100 9185 71 43 I 100 81 61 44 18 Parent 100 56 26 14 4

The two “substitution+pairwise deletion” variants tested (which bothcomprise an M202 substitution) clearly exhibit significantly improvedstability towards oxidation relative to the parent α-amylase (SEQ ID No.2).

Example 4 Determination of Thermal Stability of Variants of the Parentα-Amylases Having the Amino Acid Sequences Shown in SEQ ID No. 1 and SEQID No. 2 A: Thermal Stability of Pairwise Deletion Variants of theSequence in SEQ ID No. 1

Measurements were made using solutions of the respective variants in 50mM Britton-Robinson buffer (vide supra), pH 9.0. The solutions wereincubated at 65° C. in a water bath, and samples were withdrawn afterincubation for the indicated periods of time. The residual α-amylaseactivity of each withdrawn sample was measured using the Phadebas assay,as described above. The decline in activity was measured relative to acorresponding reference solution of the same enzyme at 0 minutes whichwas not incubated (100% activity).

The percentage of initial activity as a function of time is shown in thetable below for the parent enzyme (SEQ ID No. 1) and for the followingpairwise deletion variants in question:

Variant 1: R181*+G182* Variant 2: R181*+T183* Variant 3: G182*+G184*Variant 4: T183*+G184* Variant 5: T183*+G184*+R124P

% Activity after incubation for (minutes) Variant 0 5 10 15 30 45 60 1100 81 66 49 24 14 8 2 100 80 53 39 17 8 3 3 100 64 40 28 10 4 2 4 10064 43 34 20 8 5 5 100 78 73 66 57 47 38 Parent 100 13 2 0 0 0 0

It is apparent that all of the pairwise deletion variants tested exhibitsignificantly improved thermal stability relative to the parentα-amylase (SEQ ID No. 1), and that the thermal stability of Variant 5,which in addition to the pairwise deletion mutation of Variant 4comprises the substitution R124P, is markedly higher than that of theother variants. Since calorimetric results for the substitution variantR124P (comprising only the substitution R124P) reveal an approximately7° C. thermostabilization thereof relative to the parent α-amylase, itappears that the thermostabilizing effects of the mutation R124P and thepairwise deletion, respectively, reinforce each other.

B: Thermal Stability of Pairwise Deletion Variants of the Sequence inSEQ ID No. 2

Corresponding measurements were made for the parent enzyme (SEQ ID No.2) and for the following pairwise deletion variants:

Variant A: D183*+G184* Variant B: R181*+G182* Variant C: 0182*+G184*

% Activity after incubation for (minutes) Variant 0 5 10 15 30 A 100 8771 63 30 B 100 113 85 76 58 C 100 99 76 62 34 Parent 100 72 55 44 18

Again, it is apparent that the pairwise deletion variants in questionexhibit significantly improved thermal stability relative to the parentα-amylase (SEQ ID No. 2).

C: Thermal Stability of a Multi-Combination Variant of the Sequence inSEQ ID No. 1

Corresponding comparative measurements were also made for the followingvariants of the amino acid sequence shown in SEQ ID No. 1:

Variant 4: T183*+G184* Variant 6: L351C+M430C Variant 7: Y243F Variant8: Q391E+K444Q Variant 9: T183*+G184*+L351C+M430C+Y243F+Q391E+K444Q

% Activity after incubation for (minutes) Variant 0 5 10 15 30 4 100 6641 22 7 6 100 87 73 65 43 7 100 14 2 1 0 8 100 69 46 31 14 9 100 92 9389 82

Again, it appears that the thermostabilizing effect of multiplemutations, each of which has a thermostabilizing effect, is—at leastqualitatively—cumulative.

Example 5 Calcium-Binding Affinity of α-Amylase Variants of theInvention

Unfolding of amylases by exposure to heat or to denaturants such asguanidine hydrochloride is accompanied by a decrease in fluorescence.Loss of calcium ions leads to unfolding, and the affinity of a series ofα-amylases for calcium can be measured by fluorescence measurementsbefore and after incubation of each α-amylase (e.g. at a concentrationof 10 μg/ml) in a buffer (e.g. 50 mM HEPES, pH 7) with differentconcentrations of calcium (e.g. in the range of 1 μM-100 mM) or of EGTA(e.g. in the range of 1-1000 μM)[EGTA=1,2-di(2-aminoethoxy)ethane-N,N,N′,N′-tetraacetic acid] for asufficiently long period of time (such as 22 hours at 55° C.).

The measured fluorescence F is composed of contributions form the foldedand unfolded forms of the enzyme. The following equation can be derivedto describe the dependence of F on calcium concentration ([Ca]):

F=[Ca]/(K _(diss)+[Ca])(α_(N)−β_(N) log([Ca]))+K _(diss)/(K_(diss)+[Ca](α_(U)−β_(U) log([Ca]))

where α_(N) is the fluorescence of the native (folded) form of theenzyme, β_(N) is the linear dependence of α_(N) on the logarithm of thecalcium concentration (as observed experimentally), α_(U) is thefluorescence of the unfolded form and β_(U) is the linear dependence ofα_(U) on the logarithm of the calcium concentration. K_(diss) is theapparent calcium-binding constant for an equilibrium process as follows:

${{N—}{Ca}}\overset{K_{diss}}{\leftrightarrow}{U + {{Ca}\mspace{14mu} \left( {{N = {{native}\mspace{14mu} {enzyme}}};{U = {{unfolded}\mspace{14mu} {enzyme}}}} \right)}}$

In fact, unfolding proceeds extremely slowly and is irreversible. Therate of unfolding is a dependent on calcium concentration, and thedependency for a given α-amylase provides a measure of the Ca-bindingaffinity of the enzyme. By defining a standard set of reactionconditions (e.g. 22 hours at 55° C.), a meaningful comparison ofK_(diss) for different α-amylases can be made. The calcium dissociationcurves for α-amylases in general can be fitted to the equation above,allowing determination of the corresponding values of K_(diss).

The following values for K_(diss) were obtained for the parentα-amylases having the amino acid sequences shown in SEQ ID No. 1 and SEQID No. 2, and for the indicated α-amylase variants according to theinvention (the parent α-amylase being indicated in parentheses):

Variant K_(diss) (mol/l) D183* + G184* (SEQ ID No. 2) 1.2 (±0.5) × 10⁻⁴L351C + M430C + T183* + G184* 1.7 (±0.5) × 10⁻³ (SEQ ID No. 1) T183* +G184* (SEQ ID No. 1) 4.3 (±0.7) × 10⁻³ SEQ ID No. 2 (parent) 4.2 (±1.2)× 10⁻² SEQ ID No. 1 (parent) 3.5 (±1.1) × 10⁻¹

It is apparent from the above that the calcium-binding affinity of thelatter α-amylolytic enzymes decreases in a downward direction throughthe above table, i.e. that the pairwise deletion variant D183*+G184*(SEQ ID No. 2) binds calcium most strongly (i.e. has the lowest calciumdependency) whilst the parent α-amylase of SEQ ID No. 1 binds calciumleast strongly (i.e. has the highest calcium dependency).

REFERENCES CITED IN THE SPECIFICATION

-   Suzuki et al., the Journal of Biological Chemistry, Vol. 264, No.    32, Issue of November 15, pp. 18933-18938 (1989).-   Hudson et al., Practical Immunology, Third edition (1989), Blackwell    Scientific Publications.-   Lipman and Pearson (1985) Science 227, 1435.-   Sambrook et al., Molecular Cloning: A Laboratory Manual, 2nd Ed.,    Cold Spring Harbor, 1989.-   S. L. Beaucage and M. H. Caruthers, Tetrahedron Letters 22, 1981,    pp. 1859-1869.-   Matthes et al. The EMBO J. 3, 1984, pp. 801-805.-   R. K. Saiki et al., Science 239, 1988, pp. 487-491.-   Morinaga et al., 1984, Biotechnology, 2, pp. 646-639.-   Nelson and Long, Analytical Biochemistry 180, 1989, pp. 147-151.-   Hunkapiller et al., 1984, Nature 310, pp. 105-111.-   R. Higuchi, B. Krummel, and R. K. Saiki (1988). A general method of    in vitro preparation and specific mutagenesis of DNA fragments:    study of protein and DNA interactions. Nucl. Acids Res. 16, pp.    7351-7367.-   Dubnau et al., 1971, J. Mol. Biol. 56, pp. 209-221.-   Gryczan et al., 1978, J. Bacteriol. 134, pp. 318-329.-   S.D. Erlich, 1977, Proc. Natl. Acad. Sci. 74 pp. 1680-1682.-   Boel et al., 1990, Biochemistry 29, pp. 6244-6249.-   Deng and Nickoloff, 1992, Anal. Biochem. 200, pp. 81-88.

1. A variant of a parent α-amylase, which parent α-amylase (i) has anamino acid sequence selected from the amino acid sequences shown in SEQID No. 1, SEQ ID No. 2, SEQ ID No. 3, and SEQ ID No. 7, respectively; or(ii) displays at least 80% homology with one or more of said amino acidsequences; and/or displays immunological cross-reactivity with anantibody raised against an α-amylase having one of said amino acidsequences; and/or is encoded by a DNA sequence which hybridizes with thesame probe as a DNA sequence encoding an α-amylase having one of saidamino acid sequences; in which variant: (a) at least one amino acidresidue of said parent α-amylase has been deleted; and/or (b) at leastone amino acid residue of said parent α-amylase has been replaced by adifferent amino acid residue; and/or (c) at least one amino acid residuehas been inserted relative to said parent α-amylase; said variant havingα-amylase activity and exhibiting at least one of the followingproperties relative to said parent α-amylase: increased thermostability;increased stability towards oxidation; and reduced Ca²⁺ dependency;provided that the amino acid sequence of said variant is not identicalto any of the amino acid sequences shown in SEQ ID No. 1, SEQ ID No. 2,SEQ ID No. 3 and SEQ ID No. 7, respectively.
 2. A variant according toclaim 1, wherein at least one oxidizable amino acid residue of saidparent α-amylase has been deleted or has been replaced by a differentamino acid residue which is less susceptible to oxidation than saidoxidizable amino acid residue.
 3. A variant according to claim 2,wherein said oxidizable amino acid residue is selected from the groupconsisting of methionine, tryptophan, cysteine and tyrosine.
 4. Avariant according to claim 2, wherein said oxidizable amino acid residueis a methionine which is, or which is equivalent to, M9, M10, M105,M202, M208, M261, M309, M382, M430 or M440 of the amino acid sequenceshown in SEQ ID No.
 1. 5. A variant according to claim 4, comprising amethionine substitution which is, or which is equivalent to, one of thefollowing substitutions in the amino acid sequence shown in SEQ ID No.1: M9L; M10L; M105L; M202L,T,F,I,V; M208L; M261L; M309L; M382L; M430L;M440L.
 6. A variant according to claim 3, wherein a said methionineresidue has been replaced by threonine.
 7. A variant according to claim1, wherein at least one amino acid which is, or which is equivalent to,F180, R181, G182, T183, G184 or K185 of the amino acid sequence shown inSEQ ID No. 1 has been deleted.
 8. A variant according to claim 7,wherein the deleted amino acids are, or are equivalent to, any two ofsaid amino acid residues.
 9. A variant according to claim 8, wherein thedeletions are, or are equivalent to, R181*+G182*; or T183*+G184*.
 10. Avariant according to claim 1, comprising an amino acid substitutionwhich is, or which is equivalent to, one of the following substitutionsin the amino acid sequence shown in SEQ ID No. 1: K269R; P260E; R124P;M105F,I,L,V; M208F,W,Y; L217I; V206I,L,F.
 11. A variant according toclaim 1, comprising an amino acid substitution which is, or which isequivalent to, one of the following substitutions in the amino acidsequence shown in SEQ ID No. 1: Y243F; K108R; K179R; K239R; K242R;K269R; D163N; D188N; D192N; D199N; D205N; D207N; D209N; E190Q; E194Q;N106D.
 12. A DNA construct comprising a DNA sequence encoding anα-amylase variant according to claim
 1. 13. A recombinant expressionvector which carries a DNA construct according to claim
 12. 14. A cellwhich is transformed with a DNA construct according to claim
 12. 15. Acell according to claim 14, which is a microorganism.
 16. A cellaccording to claim 15, which is a bacterium or a fungus.
 17. A cellaccording to claim 16, which is a gram positive bacterium such asBacillus subtilis, Bacillus licheniformis, Bacillus lentus, Bacillusbrevis, Bacillus stearothermophilus, Bacillus alkalophilus, Bacillusamyloliquefaciens, Bacillus coagulans, Bacillus circulars, Bacilluslautus, Bacillus thuringiensis or Streptomyces lividans or Streptomycesmurinus, or a gram negative bacterium such as E. coli.
 18. A method ofproducing an α-amylase variant, comprising culturing a cell according toclaim 14 under conditions conducive to the production of the α-amylasevariant, and recovering the α-amylase variant from the culture.
 19. Useof an α-amylase variant according to claim 1 for washing and/ordishwashing.
 20. A detergent additive comprising an α-amylase variantaccording to claim 1, optionally in the form of a non-dusting granulate,stabilized liquid or protected enzyme.
 21. A detergent additiveaccording to claim 20, comprising 0.02-200 mg of enzyme protein per gramof the additive.
 22. A detergent additive according to claim 20, whichadditionally comprises another enzyme such as a protease, a lipase, aperoxidase, another amylolytic enzyme and/or a cellulase.
 23. Adetergent composition comprising an α-amylase variant according to claim1 and a surfactant.
 24. A detergent composition according to claim 23,which additionally comprises another enzyme such as a protease, alipase, a peroxidase, another amylolytic enzyme and/or a cellulase. 25.A manual or automatic dishwashing detergent composition comprising anα-amylase variant according to claim 1 and a surfactant.
 26. Adishwashing detergent composition according to claim 25, whichadditionally comprises another enzyme such as a protease, a lipase, aperoxidase, another amylolytic enzyme and/or a cellulase.
 27. A manualor automatic laundry washing composition comprising an α-amylase variantaccording to claim 1 and a surfactant.
 28. A laundry washing compositionaccording to claim 27, which additionally comprises another enzyme suchas a protease, a lipase, a peroxidase, an amylolytic enzyme and/or acellulase.
 29. Use of an α-amylase variant according to claim 1 fortextile desizing.